Ukraine crisis: Russian troops detain 30 Ukrainian border guards after capturing eleventh post

Move comes day after Ukrainian border patrol plane came under fire while flying near border with occupied Crimea

File image: Troops under Russian command fire weapons into the air as an approaching group of over 100 hundred unarmed Ukrainian troops at the Belbek airbase, which the Russian troops are occcupying in Crimea (Getty Images)

Russian forces further tightened their hold on Crimea early Sunday morning, capturing a Ukrainian border guard post in the west of the region, trapping and holding around 30 personnel inside.

The Chernomorskoye base on the western edge of the Back Sea peninsula was taken over without bloodshed at around 4am GMT, a border guard spokesman said.

He added that Russian forces now controlled a total of 11 border guard posts across Crimea.

The seizure comes a day after an unarmed Ukrainian border patrol plane came under fire while flying near the administrative border with Russian-occupied Crimea on an observation mission. No one was hurt.

Russian forces began taking control of the south Ukraine autonomous region 11 days ago - soon after Ukraine's pro-Russian President Viktor Yanukovich's fled the country.

Ukrainian troops are now trapped in a number of bases across Crimea, having offered no resistance - so far Kiev has held back from any action that might provoke a violent response from its neighbour. Ukraine's military, with barely 130,000 troops, would be no match for Russia's.

The US estimates that 20,000 Russian troops are in Crimea, while Moscow says it has no forces in the region beyond those normally stationed there with its Black Sea Fleet - an assertion ridiculed by the West.

The worst face-off with Moscow since the Cold War has left the West scrambling for a response, especially since the region's pro-Russia leadership declared Crimea part of Russia last week and announced a March 16 referendum to confirm it.

US Secretary of State John Kerry, speaking to Russia's foreign minister for the fourth day in a row, told Sergei Lavrov on Saturday that Russia should exercise restraint.

“He made clear that continued military escalation and provocation in Crimea or elsewhere in Ukraine, along with steps to annex Crimea to Russia, would close any available space for diplomacy, and he urged utmost restraint,” a US official said.

Speaking by phone on Saturday, US President Barack Obama assured the ex-Soviet Baltic states which have joined NATO - Latvia, Lithuania and Estonia - that the Western military alliance would protect them if necessary. Like eastern and southern Ukraine, the three all have large ethnic Russian populations.