Nato's top military commander said on Sunday that Russia had a large force on Ukraine's eastern border and said he was worried it could pose a threat to Moldova's mainly Russian-speaking separatist Transdniestria region.

Nato's Supreme Allied Commander Europe, U.S. Air Force General Philip Breedlove, voiced concern about Moscow using a tactic of snap military exercises to prepare its forces for possible rapid incursions into a neighbouring state, as it had done in the case of Ukraine's Crimea region.

Russia launched a new military exercise, involving 8,500 artillery men, near Ukraine's border 10 days ago.

"The (Russian) force that is at the Ukrainian border now to the east is very, very sizeable and very, very ready," Breedlove told an event held by the German Marshall Fund think-tank.

The president of ex-Soviet Moldova warned Russia last Tuesday against considering any move to annex Transdniestria, which lies on Ukraine's western border, in the same way that it has taken control of Crimea.

The speaker of Transdniestria's separatist parliament had urged Russia earlier to incorporate his mainly Russian-speaking region.

Transdniestria split away from Moldova in 1990, one year before the dissolution of the Soviet Union, amid fears that Moldova would shortly merge with neighbouring Romania, whose language and culture it broadly shares.

Breedlove said Nato was very concerned about the threat to Transdniestria, which he said, in Russia's view, was the "next place where Russian-speaking people may need to be incorporated."

"There is absolutely sufficient (Russian) force postured on the eastern border of Ukraine to run to Transdniestria if the decision was made to do that and that is very worrisome."

Nato had tried to make Russia a partner but "now it is very clear that Russia is acting much more like an adversary than a partner," he said.


Russia flag over 189 Ukrainian military sites in Crimea

Meanwhile, Russia said its flag is now flying over 189 Ukrainian military installations in the Crimea, the defence ministry said on Sunday, two days after President Vladimir Putin signed laws completing Russia's annexation of the Black Sea peninsula.

"The flag of the Russian Federation has been raised at 189 military units and institutions of the Ukrainian armed forces stationed on the territory of the Republic of Crimea," the ministry said in a statement, cited by news agency RIA. – Reuters