Ukraine says that a Russian armor column entered Ukraine territory Thursday night “under cover of darkness.”

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.

Russia denies sending any of its forces into Ukraine.

At the same time, President Obama was on his way to out-golf Tiger Woods.