Ukrainian military surrounded by pro-Russians
16 April 2014 Last updated at 10:30 BST
A Ukrainian military convoy - including armoured vehicles - has been barricaded by pro-Russia protesters and armed forces in the town of Kramatorsk.
The BBC's James Reynolds was watching as events unfolded and described the situation as "very unusual".
Tension is running high, with Russia's President Putin warning Ukraine is "on the verge of civil war".