Ukraine claims that two columns of tanks and military vehicles rolled into the southeastern region from Russia on Thursday after Grad missiles were fired at a border post and Ukraine’s border guards fled.

A NATO military officer claimed that “over 1,000 Russian troops are now operating inside Ukraine” and that “they are supporting separatists (and) fighting with them.”

Armoured column seen in southern Russia near Ukraine border

Armoured column seen near Ukraine border

wo columns of tanks and military vehicles rolled into southeastern Ukraine from Russia on Thursday after Grad missiles were fired at a border post and Ukraine's overmatched border guards fled, a top Ukrainian official said.

Ukrainian President Petro Poroshenko said on Thursday that Russian forces had entered his country and the military conflict was worsening after separatists swept into a key town in the east.

Poroshenko said he was cancelling a visit to Turkey and conferring with defense chiefs because of the “rapidly deteriorating situation” in the eastern Donetsk region, “as Russian troops have actually been brought into Ukraine.”

Russia says it has no involvement in the conflict between separatist militias and the Ukrainian military, in which more than 2,200 people have been killed since April.

It denies sending in weapons or troops, despite the capture of 10 soldiers inside Ukraine this week who Moscow said had probably crossed the border by accident. Russia’s envoy to the OSCE security forum in Vienna said no Russian forces were crossing the Ukrainian border “at any point.”

The latest sharp escalation in the crisis came only two days after the presidents of both countries held their first talks in more than two months and agreed to work towards launching a peace process.

Ukraine’s security and defense council said the border town of Novoazovsk and other parts of Ukraine’s southeast had fallen under the control of Russian forces.

“A counter-offensive by Russian troops and separatist units is continuing in south-east Ukraine,” it said on Twitter.

It said Ukrainian government forces had withdrawn from Novoazovsk “to save their lives” and were now reinforcing defenses in Mariupol.

Ukrainian Prime Minister Arseny Yatseniuk appealed to the United States, European Union and G7 countries “to freeze Russian assets and finances until Russia withdraws armed forces, equipment and agents”.

French President Francois Hollande said it would be “intolerable and unacceptable” if it proved true that Russian troops had entered Ukrainian territory.

Report compiled with information from Reuters and The Associated Press

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