Ukraine has asked NATO to look at all possible ways to help it protect its territorial integrity, Foreign Minister Sergei Deshchiritsya said.
The minister said he had held talks with officials from the United States and the European Union and then asked NATO for help after what Ukraine's prime minister described as Russian aggression.
A request had been made to NATO to "look at using all possibilities for protecting the territorial integrity and sovereignty of Ukraine, the Ukrainian people and nuclear facilities on Ukrainian territory," he said.
Pro-Russia activists recaptured administrative headquarters in the Ukrainian city of Donetsk and flew the Russian flag from its roof.
ITV News' Europe Correspondent describes the tense atmosphere surrounds a central government building in Donetsk .
New footage obtained by ITV News shows Russian troops firing warning shots as Ukrainian soldiers approached during a tense stand-off today.