President Vladimir Putin said Russian forces had been active in Crimea in order to support local defense forces, the first time he has admitted deployment of Russian troops on the Black Sea peninsula, Reuters reported.
"We had to take unavoidable steps so that events did not develop as they are currently developing in southeast Ukraine," Putin said in a televised call-in with the nation. "Of course our troops stood behind Crimea's self-defense forces."
A change of power took place in Ukraine on February 22.
The Verkhovna Rada (parliament) of Ukraine ousted President Viktor Yanukovych from the power, changed the constitution and scheduled presidential elections for May 25.
Yanukovych said he was forced to leave Ukraine under the threat of violence, and he remains the legally elected head of state.
A number of provinces in eastern and southern Ukraine, as well as the Crimea did not recognize the legitimacy of the Rada and decided on possibility of holding a referendum on the future fate of the regions.
The vast majority of residents of Crimea - 96 percent - voted to secede from Ukraine and join Russia, in a referendum held March 16.
With the exception of Russia most countries refused to recognize the referendum and its results.
On March 18, Russia and Crimea signed an agreement on Crimea as well as Sevastopol city joining the Russian Federation.