Armed men patrol outside of Simferopol airport in the Crimean peninsula, on February 28, 2014.
Russian aircraft carrying nearly 2,000 suspected troops have landed at a military air base near the regional capital of the restive Crimean peninsula, a top Ukrainian official has said, accusing Moscow of an "armed invasion".
"Thirteen Russian aircraft landed at the airport of Gvardeyskoye (near Simferopol) with 150 people in each one," Sergiy Kunitsyn, the Ukrainian president's special representive in Crimea, told the local ATR television channel, adding the air space had been closed.
It was not immediately clear if Russia had the right to use the base or send additional troops there under its agreements with Ukraine.