KIEV - Ukraine said on Thursday it would regard any movements by Russian military in Crimea outside the Russian Black Sea fleet's base in Sevastopol as an act of aggression.
Acting President Oleksander Turchinov issued the warning in the national parliament after armed men seized the regional government and parliament buildings in Crimea, where some ethnic Russians want the region to join the Russian Federation.
Turchinov, who is also the head of Ukraine's armed forces, appealed for Moscow to adhere to the rules of an agreement which allows Russia's Black Sea fleet to be based in Sevastopol until 2042.
"I am appealing to the military leadership of the Russian Black Sea fleet ... Any military movements, the more so if they are with weapons, beyond the boundaries of this territory (the base) will be seen by us as military aggression," he declared.
The identities of the men in the buildings in the regional capital of Simferopol were not immediately known and they issued no demands.
But witnesses said they raised the Russian flag - an act which appeared to suggest they were ethnic Russian separatists, which will add to growing alarm among Ukraine's new leaders of secessionist tendencies on the peninsula.
"Criminals in military fatigues with automatic weapons have seized the buildings," Turchinov told parliament, which had been called into session to name a new government following the ouster of President Viktor Yanukovich last Saturday.
Appealing for calm, he said he had given orders to all the security structures of Ukraine to take all necessary measures to protect its citizens.