Ukraine Navy's flagship, the Hetman Sahaidachny frigate, sets sail in the Bosphorus on its way to Black Sea in Istanbul. REUTERS/Murad Sezer

Istanbul - Two Russian warships crossed Turkey's Bosphorus Strait early Tuesday headed towards the Black Sea, Turkish media reported.

The reported ship movements came with Russia and the West locked in a standoff over Ukraine's Crimean peninsula on the Black Sea.

Turkey's state run Anatolia news agency, carrying a picture of one of the warships, said Russia had “summoned” the vessels back to its Black Sea fleet to strengthen its military presence in Crimea.

A Ukranian vessel was also seen crossing the Dardanelles Strait off Turkey's west coast and was expected to cross into the Black Sea, the agency said.

The Turkish military also said that it scrambled eight F-16 jets on Monday after a Russian spy plane was detected flying parallel to its Black Sea coast.

Turkey, a NATO ally, has repeatedly voiced fears about the fate of the Turkish-speaking Tatar minority in Crimea, which was part of the Ottoman Empire until it was conquered by Russia in the late 18th century.