Image copyright Reuters Image caption Tensions between Russia and Nato countries are high over the ongoing conflict in Ukraine 
 
 Russia is to alter its military strategy as a result of the Ukraine crisis and Nato's presence in eastern Europe, a top Russian official says. 
 
 Mikhail Popov, a Kremlin adviser, said that deteriorating relations with the US and Nato would be reflected in the updated strategy. 
 
 Nato said on Monday it would boost its presence in eastern Europe to protect its members. 
 
 Ukrainian troops are battling pro-Russian rebels in east Ukraine. 
 
 About 2,600 people have died since fighting began in April. 
 
 Ukraine's defence minister on Monday accused Russia of launching a "great war" that could claim tens of thousands of lives - claims dismissed by Russia, which denies actively supporting the rebels. 
 
 'Aggravating tensions' 
 
 Mr Popov, deputy secretary of Russia's National Security Council, told Russia's RIA news agency that "the military infrastructure of Nato member states" was "getting closer to [Russian] borders, including via enlargement". 
 
 Nato's actions were one of the key "external threats" to Russia, he said. 
 
 "Nato's planned action... is evidence of the desire of US and Nato leaders to continue their policy of aggravating tensions with Russia", Mr Popov said. 
 
 There were no details on how the doctrine might change. 
 
 Analysis - Jonathan Marcus, diplomatic correspondent 
 
 Image copyright Reuters Image caption Russia has indicated it will respond to Nato's increasing presence in eastern Europe 
 
 Almost on the eve of Nato's summit gathering in Wales, the Russian government has signalled that it will respond to Nato's plans to make preparations to deploy crisis response forces to Eastern Europe, closer to Russia's borders. 
 
 Nato insists that while there will be pre-positioned supplies and more exercises in Poland for example, these will not be permanent new bases. But that is not going to cut much ice in Moscow. 
 
 The comments by the top Kremlin security adviser Mikhail Popov has signalled that these new Nato deployments, along with missile defence plans and the Ukraine crisis, will play into a review of Russia's own defence planning. 
 
 Moscow is getting its retaliation in first with the stage set for worsening tensions between Russia and the Nato alliance. 
 
 There are growing questions now as to just how far the Kremlin is prepared to go in seeking to influence the Ukraine fighting on the ground. 
 
 Nato announced its plans on Monday for a rapid response force of several thousand troops to protect eastern European members against possible Russian aggression. 
 
 The force, to be made up of troops provided by member states on a rotating basis, would be able to be deployed within 48 hours, Nato secretary general Anders Fogh Rasmussen said. 
 
 Media playback is unsupported on your device Media caption Nato Secretary-General Rasmussen: "We must face the reality that Russia does not consider Nato a partner" 
 
 Military equipment and supplies would be pre-positioned in member states in the east so the force could "travel light, but strike hard if needed", he added. 
 
 Mr Rasmussen insisted that the plans would not breach the 1997 Nato-Russia Founding Act, which forbids the presence of permanent bases in eastern and central Europe. 
 
 The new measures are set to be approved at a Nato summit in Wales this week. 
 
 'Runway destroyed' 
 
 The Nato security alliance covers 28 member states, including Eastern European countries such as Poland and the Czech Republic. It does not include Ukraine. 
 
 Media playback is unsupported on your device Media caption David Stern reports on Ilovaysk, a town soldiers say was emptied by pro-Russian rebels 
 
 Ukraine's Prime Minister Arseny Yatsenyuk has said that he aims to put the country on the path towards Nato membership. 
 
 Russian Foreign Minister Sergei Lavrov on Tuesday said such efforts were "undermining" attempts to reach a peace deal with the rebels. 
 
 Crisis talks between Ukraine officials, rebels and Russian envoys ended without agreement on Monday. 
 
 Ukraine's army has been forced to retreat amid a series of gains by pro-Russian rebels in both the Luhansk and Donetsk regions, and further south around the port of Mariupol. 
 
 Image copyright Reuters Image caption Residents shelter from artillery fire in a basement on the outskirts of Donetsk 
 
 Image copyright Reuters Image caption The UN estimates that at least 260,000 people have been displaced in Ukraine 
 
 Military spokesman Andriy Lysenko said that 15 servicemen had been killed in the past 24 hours, with another 49 wounded. 
 
 On Monday, Ukraine's army said it had been forced to withdraw from Luhansk airport after it was attacked by Russian tanks. 
 
 The acting Luhansk region administration chief Irina Verihina told Ukraine's 112 TV: "Our troops have withdrawn, but the runway is completely destroyed. There's no way planes can land there." 
 
 The UN's refugee agency estimates that at least 260,000 people have been displaced inside the country, with most of those affected from eastern Ukraine. 
 
 Meanwhile, more than 800,000 Ukrainians, mainly ethnic Russians, have arrived in Russia since January this year, bringing the total number of people displaced by the conflict to more than a million, it added. 
 
 'I can take Kiev' 
 
 Ukrainian President Petro Poroshenko has accused Russia of "direct, overt aggression against Ukraine". 
 
 Russia has repeatedly denied Ukrainian and Western accusations that it is providing troops and equipment to the rebels. 
 
 Meanwhile, a Russian official responded to allegations that Russian President Vladimir Putin had commented: "If I want to, I can take Kiev in two weeks." 
 
 The reported comments were said to be made in a phone call to European Commission President Jose Manuel Barroso, and were reported in Italy's La Repubblica newspaper. 
 
 Kremlin adviser Yuri Ushakov told reporters that whether or not the words were spoken, the quote "was taken out of context and had a totally different meaning". 
 
 Russia's strained relations with Nato ||||| Media playback is unsupported on your device Media caption Petro Poroshenko: "It is very important that this ceasefire lasts long and that during this ceasefire we continue political dialogue to find peace and stability" 
 
 Ukraine and pro-Russian rebels in the east have signed a truce deal to end almost five months of fighting. 
 
 The two sides agreed to stop firing by 15:00 GMT and the truce appeared to be holding. But the rebels said the truce had not changed their policy of advocating splitting from Ukraine. 
 
 Meanwhile EU ambassadors have expanded a list of Russian and pro-Russian individuals targeted by sanctions. 
 
 More than 2,600 people have died since rebels stormed several eastern cities. 
 
 The takeover - which followed the annexation by Russia of the southern Crimea peninsula in March - prompted a military operation by Ukrainian forces to retake the cities. 
 
 The rebels, who had largely been pushed back towards their strongholds of Donetsk and Luhansk, made new advances in recent days. 
 
 Image copyright AFP Image caption Residents around Donetsk have been taking shelter in schools and other buildings for weeks 
 
 Image copyright Reuters Image caption Petro Poroshenko welcomed the ceasefire during a news conference at the Nato summit in Wales 
 
 Earlier in the day, fighting was reported around Donetsk and Mariupol, a coastal city about 110km (70 miles) to the south. 
 
 Witnesses said three large explosions were heard in Donetsk just before the ceasefire came into force. 
 
 At the scene: Fergal Keane, BBC News in Mariupol 
 
 Media playback is unsupported on your device Media caption As Fergal Keane reports, casualties continued in Ukraine in the hours before the ceasefire 
 
 There are rumours that Ukrainian battle tanks have pulled back from the eastern edge of the city. The rebels are holding their positions outside Mariupol. 
 
 It is all in dramatic contrast to the day's beginning. Before dawn I was woken by the noise of explosions as government and pro-Russian forces fought an artillery duel. 
 
 The sound of rockets, air strikes and mortars continued to be heard throughout the morning. Large plumes of smoke dotted the fields around the east of the city. 
 
 One of those explosions claimed the lives of Lubov Vasylivna's grandchildren: 10-year-old Nikita, who was disabled, and his six-year-old sister, Karolina. 
 
 They died just hours before the ceasefire came into effect. "I don't know how I am going to survive this," Lubov told me. "The images of them are in front of my eyes." 
 
 Querying Nato's rapid reaction force 
 
 Image copyright AFP Image caption Cities such as Mariupol have been the scene of fierce fighting in the past few days 
 
 But later reports suggested fighting in both cities and elsewhere in the region had subsided. 
 
 The West accuses Russia of sending arms and troops to back the rebels in eastern Ukraine - allegations denied by Russia. 
 
 The ceasefire talks in Minsk, Belarus, were brokered by the Organization for Security and Cooperation in Europe (OSCE), and involved a former Ukrainian president, leaders of the pro-Russian rebels, and a Russian delegate. 
 
 Both sides agreed to stop fighting, and the OSCE said it would monitor the ceasefire. However, the full agreement has not been published. 
 
 President Petro Poroshenko said the ceasefire was based on a 12-point peace plan that included the release of "hostages", which he said would probably happen on Saturday. 
 
 "It is very important that this ceasefire lasts long, and during this ceasefire we continue the political dialogue to bring peace and stability," he said. 
 
 Media playback is unsupported on your device Media caption "The only reason that we're seeing this ceasefire... is because of both the sanctions that have already been applied and the threat of further sanctions" 
 
 Russian President Vladimir Putin had been told of the plan during a phone call, he added. 
 
 In another development, Nato agreed to form a multi-national "spearhead" force capable of deploying within 48 hours. 
 
 At the close of a two-day summit in Wales, Nato chief Anders Fogh Rasmussen said Russia's actions in Ukraine had been a wake-up call for the alliance, and had spurred the formation of the rapid-reaction force. 
 
 He welcomed the ceasefire, saying he hoped it "could be the start of a constructive political process". 
 
 However, Russia's foreign ministry reacted angrily to Nato's announcements. 
 
 "The essence and tone of [Nato] statements on the Ukraine situation, and the plans announced to hold joint Nato exercises with Kiev on the territory of that country before the end of 2014, will inevitably lead to heightened tension," a statement said. 
 
 "They risk wrecking the progress made in the peace process in Ukraine, and encourage a deepening of the split in Ukrainian society." 
 
 Sanctions 
 
 European Commission President Jose Manuel Barroso said in a statement on Friday that the EU had expanded the list of persons under an EU asset freeze and travel ban to include the new leadership in eastern Ukraine, the Crimean government and Russian decision-makers and oligarchs. 
 
 The sanctions are due to be formally adopted on Monday. However, diplomats quoted by Reuters said the measures could be suspended if the ceasefire held and if Moscow withdrew forces from Ukraine. 
 
 Earlier, US President Barack Obama said the ceasefire had been agreed because of sanctions imposed on Russia. 
 
 Measures against Russia would be reviewed in line with the implementation of the ceasefire, which he said would be a very long process. ||||| Stephen Harper is heading to a crucial summit of NATO leaders where the Western military alliance will give itself the power to respond to threats more quickly in the face of Russia’s continued effort to destabilize and break up Ukraine. 
 
 NATO leaders are set to approve a rapid-reaction military force, drawn from their respective defence capabilities, that could be deployed to a crisis in Eastern Europe within two days, alliance officials say. This “spearhead” unit would have a permanent command centre staffed by rotating alliance members as well as supply depots located in various regions so troops would not have to fly in all their equipment. 
 
 “This spearhead … could include several thousand troops, ready to respond where needed with air, sea and special-forces support,” NATO Secretary-General Anders Fogh Rasmussen told a news conference Monday in Brussels. 
 
 NATO’s existing response force takes five days for the first units to arrive. 
 
 This summit, originally meant to mark the end of the NATO-led mission in Afghanistan, will instead signal a shift to the defence of Europe as the alliance’s central concern once more. 
 
 Mr. Harper departed Ottawa Tuesday morning for the U.K. He'll first visit London‎ to promote bilateral trade and investment in light of the Canada-European Union free-trade deal and then proceed to a Cardiff-area resort in Wales for talks with NATO member country leaders. 
 
 The rapid-response force would not help Kiev, which has been battling pro-Moscow rebels for months after Russia unilaterally seized Crimea this spring and now has Vladimir Putin pressuring it to discuss “statehood” for southeast regions of Ukraine. 
 
 Canadian officials, speaking on background, made it clear that the North Atlantic Treaty Organization has no plans to deploy troops to Ukraine, which is currently taking steps to apply for membership in the Western military alliance. It’s unclear if, or when, Kiev might be admitted into the club, which has an agreement to defend member countries against attack. 
 
 NATO appears to have shelved a proposal to permanently station alliance troops in new bases along its eastern flank, a measure sought by members such as Poland as a means of providing a deterrent to further Russian aggression. Member countries such as Germany rejected the idea because such a move could provoke Moscow. 
 
 The rapid-reaction force, which could serve as a deterrent in its own right, appears to be a compromise. NATO officials said the force could grow from a small number to as large as a brigade, which would mean between 3,000 and 5,000 troops. It means NATO would be ready to quickly respond to Russian aggression that goes beyond Ukraine, which the alliance has confirmed with satellite imagery is now fighting Russian troops, and not just pro-Moscow rebels, on its own soil. 
 
 Canada will be asked to contribute soldiers and equipment to NATO's new high-alert force. 
 
 But the Canadian government refused to say Monday whether it would contribute on a regular basis to this rapid-reaction force, with officials saying only they would “consider all measures accordingly and look forward to discussions at the summit.” 
 
 The alliance, said Fen Hampson, director of the Global Security and Politics program at the Centre for International Governance Innovation in Waterloo, Ont., “is divided between its East European and Baltic members who are deeply worried that Putin won’t stop with Ukraine if he gets what he wants, and its major powers, Germany, the U.K. and France, who continue to believe that Putin is amenable to negotiation and persuasion.” 
 
 Canada was also wary of the proposal to permanently station NATO troops in new bases because there was insufficient detail on which allies might pay the bills or contribute troops and what the rules of engagement would be. “None of that was clear,” a Canadian official said. 
 
 The Harper government, expected to go to the polls in 2015, is also balking at a push for NATO countries to boost military spending to at least 2 per cent of gross domestic product. The British government is calling for this commitment at the summit. Britain is among a small minority of NATO members that currently spend 2 per cent or more of GDP on defence, while Canada spends roughly 1 per cent. 
 
 Canadian officials defend their position, saying the NATO pledge goes beyond what Canadian taxpayers would support. They say Canada shouldered a big burden with its decade-long Afghanistan deployment and its contribution to Operation Protector in Libya. 
 
 The Harper government has chopped military spending to balance the books, and a recent study said on an inflation-adjusted basis that Canada’s defence budget is now smaller than it was in 2007. 
 
 Ottawa has a ship, six fighter jets and rotating shifts of Canadian Armed Forces members on training exercises in Europe to help reassure NATO member countries concerned about further Russian aggression in the region. It’s also matched sanctions imposed on Russians and Ukrainians linked to Moscow’s efforts to menace Ukraine. 
 
 Mr. Hampson said the summit marks a watershed moment for the alliance. “NATO is facing its greatest crisis since the Berlin and Cuban crises of the Cold War,” he said. “NATO can show that it is a real alliance that is prepared to stand up to Putin’s incursions, or it can fade into oblivion by issuing more frothy communiqués that commit its members to little.” 
 
 Editor's note: An earlier version of this article stated incorrectly that the next federal election is in 2016. This version has been corrected to say the vote is in 2015.
– Tough talk as NATO-Russia relations continue to deteriorate: NATO leaders, who meet in the UK later this week, are planning a "rapid reaction" force that can deploy to Russia's worried Eastern European neighbors within 48 hours, reports the New York Times. The "spearhead" force would have a permanent command center to allow it to respond swiftly to threats, the Globe and Mail notes. "This spearhead ... could include several thousand troops, ready to respond where needed with air, sea, and special-forces support," NATO Secretary-General Anders Fogh Rasmussen told reporters. The NATO summit in Newport, Wales, is especially important because "Russia thought it can change the borders of a sovereign European country by force, and this is happening not very far from NATO's borders," says Estonian Prime Minister Taavi Roivas, calling for fresh plans to ensure all members of the alliance are "equally and strongly protected." Russian defense chiefs, meanwhile, say NATO's actions are "evidence of the desire of US and NATO leaders to continue their policy of aggravating tensions with Russia" and that Moscow plans to craft a new military doctrine in response to NATO plans and the Ukraine crisis, the BBC reports. In Ukraine, President Petro Poroshenko accused Russia of "direct and undisguised aggression" yesterday as government forces continued to suffer reverses, including a retreat from the Luhansk airport, where the Ukrainian military says a Russian tank battalion supported pro-Russia rebels, Reuters reports.