'If it means a bullet to the head, then it's a bullet to the head': Ukrainian opposition threaten to go on the attack if president does not strike deal Boxer was on the streets of Kiev pleading with both police and protesters to uphold the fragile peace He promised to return at 8pm local time to announce the results of negotiations with President Yanukovych The protesters extinguished piles of burning tyres that had been sending thick black smoke towards police lines The three main opposition issued an ultimatum to the president to dismiss the government and call an election Demonstrators had hurled rocks and Molotov cocktails with police responding with tear gas and rubber bullets Opposition leader Arseniy Yatsenyuk said President Viktor Yanukovych had 24 hours to agree a peaceful solution Boxer turned politician Vitali Klitschko has brokered an uneasy truce on the streets of Kiev following days of violent demonstrations in the Ukraine capital which have reportedly left five people dead. At midday Kiev time, Klitschko announced the truce to crowds in the city's Independence Square. He said he would return at 8pm to announce the results of ongoing negotiations between opposition leaders and President Yanukovych. At Klitschko's request, protesters extinguished burning tyres that had been sending thick clouds of putrid smoke toward police lines. An ultimatum issued by the opposition to the president to call an election was set to expire this evening with no sign yet of a compromise. Three main opposition leaders had urged protesters to refrain from violence for 24 hours until their ultimatum to President Viktor Yanukovych expired. They demanded that he dismiss the government, call early elections, and scrap harsh anti-protest legislation that triggered violence at a demonstration on Sunday. Former world heavyweight champion boxer and leader of the opposition Udar party Vitali Klitschko addresses protesters in Kiev's Independence Square Opposition leader Vitali Klitschko greets pro-European integration protesters at the site of clashes with riot police in Kiev Tomorrow we will go forward together. And if it's a bullet in the forehead, then it's a bullet in the forehead, but in an honest, fair and brave way,' declared one of them, Arseniy Yatsenyuk. Klitschko, a member of parliament since December 2012 and the leader of the Ukrainian Democratic Alliance for Reform party, was on the streets in the capital's Independence Square pleading with both police and protesters to uphold the peace until the ultimatum expires. He said that Yanukovych should start by releasing protesters who were detained. 'We are demonstrating our willingness to find a compromise, but the government needs to make its step in turn,' he told the crowds. On Wednesday, riot police beat and shot at protesters, volunteer medics and journalists, resulting in the deaths of two demonstrators - the first casualties of the clashes. The opposition contended that as many as five people died. The Interior Ministry said Thursday that 73 people have been detained, 52 of them being investigated for 'mass riots' - a recently created criminal charge that carries a prison sentence of up to eight years. Allegations that activists have been abducted and even tortured by police have spread. Turmoil: Protestors clash with police in Kiev, last night after opposition leaders warned the government must agree to a peaceful solution or expect further violence Fuel: A protester prepares to throw tyres onto a fire separating demonstrators from riot police in central Kiev today Standoff: A bare-chested protestor confronts a line of riot police during violent clashes last night. At least two people were killed as demonstrations against the government's decision not to sign a deal with the European Union continued Firebomb: A demonstrator uses a catapult to fire a Molotov cocktail into lines of riot police in Kiev's Independence Square The largely peaceful protests against Yanukovych's decision to shun the European Union and turn toward Moscow in November descended into violence on Sunday when demonstrators, angered by last week's passage of repressive laws intended to stifle protests, marched on official buildings. For days protesters hurled fire bombs and stones at police, who retaliated with stun grenades, tear gas and rubber bullets. The United States has responded by revoking the visas of Ukrainian officials linked to violence and threatened more sanctions. German Chancellor Angela Merkel said her nation doesn't think this is the time to consider sanctions against the Ukrainian government, adding that the current priority is 'ensuring that channels of communication are opened up and that the Ukrainian government complies with its obligations to secure fundamental democratic rights'. 'We are extremely concerned - not just concerned, appalled - about the way in which laws have been pushed through that raise questions over these fundamental freedoms,' Merkel said. Protesters stand behind a defensive barricade as they set off fireworks towards the police Violent clashes: A protester prepares to throw a Molotov cocktail during clashes with police in central Kiev last night A protester prepares to hurl a rock against police lines as a fire billows black smoke into the sky A protestor throws a petrol bomb towards the police during protests in Kiev yesterday A protester lights a petrol bomb before firing into the police using a large slingshot EU Commission President Jose Manuel Barroso said that if the situation in Ukraine does not stabilize, the EU "would assess possible consequences in its relationship," according to spokesman Olivier Bailly. Barroso also said he had received assurances from Yanukovych that he did not foresee the need for imposing a state of emergency in Ukraine. Russia in turn has accused the West of meddling in Ukraine's affairs. 'We feel regret and indignation about the obvious foreign interference in the developments in Kiev,' Russian President Vladimir Putin's spokesman Dmitry Peskov told the daily Komsomolskaya Pravda in an interview published Thursday. Former Soviet President Mikhail Gorbachev released a letter to Putin and President Barack Obama prodding them to help broker talks to end the crisis. 'The situation is such that without help, without assistance of authoritative representatives of our two countries it may lead to a catastrophe,' said the letter posted on the Gorbachev Foundation's website. Kiev: Protesters burned tyres sending plumes of black smoke billowing into the air as they faced riot police using tear gas, stun grenades and rubber bullets Casualties: Five activists were killed and around 300 wounded in yesterday's clashes. Four of the dead were reportedly killed by gunshot wounds Frontline: Demonstrators fortified their positions overnight using sandbags filled with snow while riot police held their line in central Kiev in a tense face-off The violent protests have been raging in the Ukrainian capital since January 19, following the government's decision not to sign a deal for closer integration with the European Union Burning: A protester clasps a rock as he sets fire to a tyre in the Ukraine capital Kiev's Independence Square last night A protester uses a slingshot to launch a rock at police in central Kiev today A 20-year-old ethnic Armenian who joined the protests in December after traveling from his home in the eastern city of Dnipropetrovsk, stands on a barricade in Kiev, Ukraine Missiles: A protester aims fireworks at police during clashes, in central Kiev Thick black smoke from burning tyres engulfed the downtown Ukrainian capital as an ultimatum issued by the opposition to the president to call early election or face street rage was set to expire with no sign of a compromise A protester stands at a burning barricade between police and protesters in central Kiev Tensions remained high in Kiev, as protesters said they would give peace a chance - but not for long. 'We're ready to wait so that new victims don't appear,' said 30-year-old demonstrator Anatoly Lovchenko. 'But if the government doesn't listen to our demands, we'll start up again.' The three main opposition leaders, who addressed the crowds in the square after meeting the president on Wednesday vowed to lead the demonstrators in battles with police, if their demands are not met. If Yanukovych doesn't concede, The bloody clashes marked a new peak in tensions following two months of protests over the government's failure to sign a deal for closer integration with the Europe under Russian pressure. Five activists have reportedly been killed in the protests. Four of the dead were reportedly killed by gunshot wounds. Around 300 were believed to have been wounded in yesterday's clashes. Violence: Protesters clash with police in central Kiev, Ukraine, as city health officials and police said that two people died of gunshot wounds during the clashes earlier today Demonstrators set tyres on fire and threw stones and the police responded with stun grenades, rubber bullets and tear gas In flames: A protester throws a Molotov cocktail during an anti-government protest in downtown Kiev A man carries a burning-tyre during a rally held by pro-European protesters in Kiev Eruption: Protesters throw rocks at police in central Kiev, Ukraine, as city health officials and police said that two people died of gunshot wounds during the clashes on Wednesday morning Struck: A security officer struggles with his helmet moments after being engulfed in flame after being hit by a Molotov cocktail On Wednesday night, demonstrators fortified their positions using sandbags filled with snow. Riot police were still holding their line on Grushevsky Street in central Kiev as hundreds of protesters faced them on the other side of barricades. Tens of thousands of people had filled Independence Square in Kiev, the main protest hub for the last two months, hoping their sheer numbers would deter any attempt by police to disperse the rally. Police had on Wednesday upped the stakes in the protests by launching a major assault, initially pushing demonstrators back well beyond their initial lines by marching forward in military formation. But the protesters then regrouped, creating a semi-circle of new barricades out of burning black tyres whose flames burned in near-apocalyptic scenes. Police in formation ready to tackle demonstrators against the government's anti-protest law Three people were reported dead in Kiev on Wednesday morning, during clashes between police and demonstrators A demonstrator holds up a chain and a riot police shield as protestors clash with police Police on Wednesday upped the stakes in the protests by launching a major assault, initially pushing demonstrators back well beyond their initial lines by marching forward in military formation A demonstrator holds a hand gun as protesters clash with police in the center of Kiev In flames: A protester throws a Molotov cocktail during an anti-government protest in downtown Kiev, last night Inna Bogoslovska, a former MP from Yanukovych's Region's Party who switched sides during the protest, bluntly told the rally on Independence Square the authorities were doomed: 'Viktor Fyodorovich, this is the end,' she said. The ongoing violence has horrified Ukrainians, who have never witnessed such scenes in their country including during the 2004 Orange Revolution which was almost entirely peaceful. Amid calls for sanctions against the Ukrainian government, European Commission president Jose Manuel Barroso warned the authorities that the EU executive authority would assess 'possible actions' against the Ukrainian authorities. The United States also revoked the visas of several Ukrainian nationals linked to violence against protesters in November and December last year, the US embassy said in a statement. Brutal: Police troops beat a protester holding the national flag during anti-government protests in Kiev that are thought to have left three men dead Clampdown: Police detain protesters during a clash in central Kiev, today as both sides appear unwilling to back down from violent conflict Help: An armoured officer attempts to help a comrade who has been hit by a flaming projectile setting his clothing on fire War zone: Ukrainian riot police stand in formation during an anti-government protest Attacks: Protesters have pelted officers with rocks, which can be seen here in front of a defensive formation Stand-off: Demonstrators, who now face with harsh new laws, square off against lines of riot police But Russia, which has regarded Ukraine's pro-EU protest movement with suspicion from the start, took a different view and blamed the opposition and West for the clashes. 'Ukraine's legitimate authorities face outside interference in its internal affairs,' Russian Deputy Foreign Minister Grigory Karasin told the Interfax news agency, referring to EU and US statements. But President Vladimir Putin's spokesman Dmitry Peskov said Thursday that Russia will not intervene in the protests and believes Ukraine's leadership will find a way out. We consider we do not have the right to intervene in any way in the internal affairs of our brother Ukraine. That's unacceptable and Russia has not done this and will not do it,' Peskov said in an interview published on the website of Komsomolskaya Pravda daily.