Ukrainian forces and pro-Russian separatists were locked in a fierce battle in the rebellious east of the country yesterday, Ukrainian military sources said.

The sources said there were reports that tanks had been deployed by both sides but this could not immediately be confirmed. One military source said heavy fighting broke out at around 4am near the town of Krasny Liman, which has been under government control since early this month, and that separatists in the area appeared to have tried to break through a cordon of government troops.

“There’s a major battle going on which exceeds in terms of force and scale anything there has been up to now,” the military source said.

Dmytro Tymchuk, a military analyst who has good sources in the military, said separately that fighting had begun when separatists refused a call for them to lay down their arms in line with a peace plan outlined by President Petro Poroshenko.

We now see a new Russian military build-up around the Ukrainian border

Up to 4,000 separatist fighters could be involved and armoured vehicles, possibly tanks, were being used by each side, the military source said.

“The anti-terrorist operation is continuing. There is a battle going on,” government forces spokesman Vladyslav Seleznyov said.

Asked about the report that 4,000 separatists could be involved, Seleznyov replied: “Then, there’ll be 4,000 coffins”.

Meanwhile Nato Secretary-General Anders Fogh Rasmussen said yesterday that at least a few thousand more Russian troops were now at Ukraine’s eastern border, a build-up he called a regrettable step backwards.

After Moscow annexed Ukraine’s Crimea region in March, Nato said Russia had massed some 40,000 troops near the Ukrainian border. It withdrew the vast majority of them until just one unit and 1,000 troops remained about a week ago.

“We now see a new Russian military build-up around the Ukrainian border. At least a few thousand more Russian troops are now deployed,” Rasmussen said in London.

“I consider this a very regrettable step backwards. It seems Russia keeps the option open to intervene further in Ukraine,” he said. “The international community would have to respond in a firm manner if Russia were to intervene further in Ukraine.”

He added: “That would imply deeper... economic sanctions against Russia which would have a very damaging effect on the Russian economy.”

In last few days, Nato has seen evidence of a few mechanised units, consisting of a few thousand Russian troops, conducting new troop movements close to the Ukrainian border.

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