And at Crimea's Belbek air base in Sevastopol, pro-Russian troops who have seized it fired warning shots into the air to prevent around 300 Ukrainian soldiers approaching, the Associated Press news agency reports.

The group, carrying a Ukrainian flag and a red flag of their unit walked onto the airfield about half a kilometer away from the runway.

They were surrounded by at least five Russian military vehicles and at least 50 Russian troops who are taking strategic positions around them, including on the ground. They are armed with sniper rifles and machine guns, some of which are constantly pointed at the group of the Ukrainian soldiers.

The two groups have peace time until 12 o'clock noon, by which time the Russian troops expect the Ukrainian troops to surround.

The situation is extremely tense. A handful of wives of the Ukrainian soldiers are waiting for developments outside the airfield.