Heaviest shelling since truce renews Ukraine war fears Clashes between government forces and Russian-backed separatists in Ukraine's breakaway eastern regions intensified this weekend, as Kiev accused Moscow of supplying rebels with heavy weaponry and new fighters. Observers in Donetsk and other cities along the perimeter of rebel-held regions reported some of the heaviest shelling since the September 5 ceasefire agreed in Minsk, which has been repeatedly violated through sporadic skirmishes and artillery fire. The renewed fighting threatens the shaky truce in the seven month-old military conflict and comes amid claims by Kiev that Russia has stepped up inflows of heavy weaponry and fighters across the region's porous rebel-controlled border. The escalation also follows a warning from former Soviet leader Mikhail Gorbachev on the eve of the 25th anniversary of the fall of the Berlin Wall that the Ukraine crisis could plunge the east and west into a new cold war. Colonel Andriy Lysenko, a Ukrainian army spokesperson, on Sunday accused separatists of stepping up attacks on Ukrainian positions. "The past week was characterised by an increase in the intensity of shelling and the transfer of additional force - ammunition, equipment and personnel - to terrorist groups," he said. Despite mounting evidence, Russia has denied claims by Kiev and the west that it is arming and using local pro-Russian rebels to conduct a creeping proxy invasion into Ukraine's industrial eastern heartland. More than 4,000 people have died since protests in the Donetsk and Lugansk regions erupted into violence in March. In a statement this weekend, a Donetsk-based monitoring mission of the Organisation for Security and Co-operation in Europe said it had observed "heavy, outgoing shelling to the north and northwest of the city's outskirts" as well as convoys of dozens of unmarked "heavy weapons and tanks . . . containing personnel in dark green uniforms without insignia." The description resembles the so-called "green men" who appeared throughout Crimea and took over military installations and government buildings in March before Russia's annexation of the peninsula following an internationally unrecognised referendum. Mr Lysenko claimed the convoys arrived from Russia. "Although the OSCE did not specify to whom the equipment and soldiers belonged, the Ukrainian military has no doubt of their identity," he said. Federica Mogherini, the EU's foreign policy chief, on Sunday described the OSCE's findings as "a very worrying development" adding "it is imperative to avoid any re-escalation of hostilities." "I call on the Russian Federation to fully assume its responsibilities in this regard, including by preventing any further movement of military, weapons or fighters from its territory into Ukraine, and withdrawing any troops, weapons and equipment under its control from Ukraine," she said in the statement. Moscow has remained defiant in the face of recriminations from Kiev and the west, accusing the US and EU of stoking tensions in Ukraine by supporting the country's pro-western geopolitical shift. In a speech last month President Vladimir Putin said the US risked undermining the post-cold war world order and called for a redesign of the system of global governance along "multipolar" lines. Shinzo Abe, Japan's prime minister, "strongly urged" Mr Putin to play a constructive role in ensuring that both sides abide by the ceasefire in bilateral talks held on the sidelines of the Asia Pacific Economic Co-operation leaders summit this weekend. In the clearest sign yet that Russia's economy is straining under western sanctions imposed for its aggression towards Ukraine, the rouble has tumbled sharply in recent weeks, declining some 8 per cent against the dollar in the past week alone.