Armed men thought to be Russians drove a truck into a Ukrainian missile-defense post in the Crimea region on Friday and took it over without a shot being fired, a Reuters reporter on the scene said.
Initial reports said the truck had smashed through the gates of the base in the port city of Sevastopol and that it was being stormed, but the reporter could not see any signs of major damage to the gates and the base was quiet.
A Ukrainian military official, Vladislav Seleznyov, said by telephone that the armed men took over the base without any shooting and that no one was hurt.
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Another Ukrainian military official told Reuters at the post that the armed group inside had not seized any weapons and said he was mediating between the sides.
Crimea's pro-Russia premier, Sergei Aksyonov, was asked about the incident during a political chat show being shown live on Ukrainian television. He said all was calm at the military post.
Russian forces have taken over some military installations and other buildings on the peninsula, where Russia's Black Sea Fleet has a base, but both sides have held their fire.