Crimea's newly elected Prime Minister has asked Russian authorities for help in maintaining peace in the region.
"I appeal to the president of the Russian Federation, Vladimir Putin, to provide assistance in ensuring peace and tranquillity on the territory of the Autonomous Republic of Crimea," Sergey Aksyonov said in a statement.
Mr Aksyonov, who was appointed by the Crimean parliament on Thursday, also said he was taking control of Crimea's interior ministry, armed forces, fleet and border guards "on a temporary basis".
"All commanders are to obey only my orders and instructions," Mr Aksyonov said. "I ask all those who refuse to do so to resign."
The new cabinet in Ukraine is due to meet for the first time on Saturday to discuss the deepening crisis over Russia's reported military deployments, BBC reports.
On Friday unknown militants took over airports in the Crimean capital, Simferopol, and Sevastopol, where Russia's Black Sea Fleet is based,
Ukrainian media citing local officials said 13 Russian aircraft carrying nearly 2,000 suspected troops had landed at a military air base near Simferopol. The report remains unconfirmed.