REUTERS/Vasily Fedosenko Uniformed men, believed to be Russian servicemen, stand guard outside a Ukrainian military base in the village of Perevalnoye outside Simferopol, March 7, 2014.
Serhiy Astakhov, aide to the head of border guards service, told Reuters the figure was an estimate and included both troops that had arrived since last week and Russia's Black Sea Fleet, permanently based in the Crimean port of Sevastopol.
Russia, whose forces occupied the isolated peninsula last week, says the only troops it has there are those based in Sevastopol. The Russian troops that have occupied positions across Crimea wear no insignia on their uniforms but drive vehicles with Russian military plates.
Ukraine says thousands of extra troops have arrived and have fanned out across the occupied peninsula in violation of the treaty governing the base. Earlier this week Ukraine said there were a total of 16,000 Russian troops in Crimea.
(Editing by Jon Boyle)