President Vladimir Putin flew in to Crimea yesterday for the first time since it was annexed by Moscow, proclaiming as he marked the Soviet victory in the Second World War that incorporating the former Ukrainian territory had made Russia stronger.

EU leaders united in agreeing to include a dozen more Russian politicians and senior advisers in the Kremlin on their blacklist, but discussions on the next steps were proving more difficult last night at their two-day summit.

Russian forces tightened their grip on Crimea yesterday despite a US warning to Moscow that annexing the southern Ukrainian region would close the door to diplomacy in a tense East-West standoff.

President Vladimir Putin delivered a robust defence of Russia’s actions in Crimea and said he would use force in Ukraine only as a last resort, easing market fears yesterday that East-West tension over the former Soviet republic could lead to war.

Ukrainian president Viktor Yanukovich said last night he had agreed a “truce” with opposition leaders, after street violence in which at least 26 people were killed, and a start to negotiations to end further bloodshed.