Kiev says forces shelled Russian armour inside Ukraine

 Ukraine said its artillery partly destroyed a Russian armoured column that entered its territory overnight and said its forces came under shellfire from Russia on Friday in what appeared to be a major military escalation between the ex-Soviet states.

Russia's government denied its forces had crossed into Ukraineand accused Kiev of trying to sabotage deliveries of aid. NATO said there had been a Russian incursion into Ukraine, while avoiding the term invasion, and European capitals accused the Kremlin of escalating the fighting.

Kiev and its Western allies have repeatedly accused Russia of arming pro-Moscow separatist rebels in eastern Ukraine, and of sending undercover military units onto Ukrainian soil.

But evidence of Russian military vehicles captured or destroyed on Ukrainian territory would give extra force to Kiev's allegations - and possibly spark a new round of sanctions against the Kremlin.

Andriy Lysenko, a spokesman for the Ukrainian military, told a news briefing that Kiev's forces had picked up a Russian military column crossing the border under cover of darkness.

"Appropriate actions were undertaken and a part of it no longer exists," Lysenko said.

Ukrainian President Petro Poroshenko briefed British Prime Minister David Cameron on the incident and told him a "significant" part of the Russian column had been destroyed, according to statement from Poroshenko's office.

Britain summoned Russia's ambassador to ask him to clarify reports of a military incursion into Ukraine, and European Union foreign ministers said any unilateral military actions by Russia in Ukraine would be a blatant violation of international law.

NATO

Earlier on Friday, responding to reports that a Russian column had entered Ukraine overnight, NATO Secretary-General Anders Fogh Rasmussen said the alliance had seen what he called a Russian incursion into Ukraine.

"It just confirms the fact that we see a continuous flow of weapons and fighters from Russia into eastern Ukraine and it is a clear demonstration of continued Russian involvement in the detribalization of eastern Ukraine," the NATO chief said.

A spokesman for Russia's border guard service was quoted by Russian news agencies as denying that any Russian military units had entered Ukraine.

In a statement issued by the Russian foreign ministry, Moscow accused Ukrainian forces of intensifying the fighting against pro-Moscow separatists in eastern Ukraine in an attempt to sabotage Russian efforts to get aid into rebel-held areas.

After Ukraine reported the clash, Russia's rouble currency weakened against both the dollar and the euro. Russian shares were also dragged lower.

The dollar hit a three-week low against the safe-haven Swiss franc CHF=, benchmark German 10-year Bund yields DE10YT=TWEB fell about 4 basis points to a new record low of 0.962 percent and European stocks .FTEU3 sold off, led by the Russia-exposed German DAX index .GDAXI.