Ukrainian President Petro Poroshenko accused Russia on Monday of "direct and undisguised aggression" which he said had radically changed the battlefield balance as Kiev's forces suffered a further reverse in their war with pro-Moscow separatists.
In the latest in a string of setbacks in the past week, Ukraine's military said it had pulled back from defending a vital airport in the east of the country, near the city of Luhansk, where troops had been battling a Russian tank battalion.
Poroshenko said in a speech there would be high-level personnel changes in the Ukrainian armed forces, whose troops fled a new rebel advance in the south which Kiev and its Western allies say has been backed up by Russian armoured columns.
Russian President Vladimir Putin, who called on Sunday for immediate negotiations on the "statehood" of southern and eastern Ukraine, blamed Kiev's leadership for refusing to enter into direct political talks with the separatists.
European Union leaders decided at a summit on Saturday that the direct engagement of Russian troops in the war - still denied by the Kremlin - called for a stepping up of economic sanctions unless Moscow pulled its soldiers back.
With German Chancellor Angela Merkel stressing that accepting Russia's behaviour was not an option, EU ambassadors were to start discussing a new package of measures that could include a ban on Europeans buying Russian government bonds, EU sources said.
Until last week Ukraine had appeared close to crushing the four-month rebellion in the east, which erupted after a pro-Moscow president was forced out of power by popular protests. But then the rebels opened a new front to the south on the coast of the Sea of Azov, pushing towards the city of Mariupol.
Aggression
Poroshenko repeated Kiev's belief that Russian forces are helping the rebels to turn the tide of the war. "Direct and undisguised aggression has been launched against Ukraine from a neighbouring state. This has changed the situation in the zone of conflict in a radical way," he said in his speech at a military academy in Kiev.
Defence Minister Valery Heletey added on his Facebook page that Ukraine no longer faced a threat from separatists but outright war with Russian troops. "Unfortunately, in such a war, the losses will be numbered not in their hundreds, but in thousands, even tens of thousands," he said. "We must refrain from panic and show that Ukrainians are not about to surrender." In the Belarussian capital, Minsk, separatists sat down for preliminary peace talks with Ukraine, saying they would be prepared to stay part of Ukraine if they were granted "special status", according to Russian news agencies.
But they said one of their key conditions would be for Kiev to immediately end its military offensive.
The separatists' demands did not appear, at first sight, to be acceptable to Kiev since they would leave the rebels in control of the territories of Ukraine's industrialised east and exercising a trade policy tilted towards Russia and away from integration with the European Union, which is Kiev's key aim.
Military spokesman Andriy Lysenko said Ukrainian forces had pulled back from the airport near Luhansk. However, they had destroyed seven Russian tanks and identified a major build-up of Russian forces to the north and south of the city.
