(Adds seizure of third warship)

SEVASTOPOL, Ukraine, March 20 (Reuters) - Russian troops took over three Ukrainian warships in Crimea on Thursday, a Ukrainian navy official said, after Moscow's military seizure of the Black Sea peninsula and annexation of the territory.

Vladislav Seleznyov, a Ukrainian military spokesman in Crimea, said the Russian forces used stun grenades as they stormed the corvette Ternopol in the port city of Sevastopol.

The Russian national tricolour and the Russian navy's flag were flying on a pier elsewhere in Sevastopol where two more Ukrainian navy corvettes were anchored, indicating they were seized.

There were no flags on display on the sterns of the corvettes - called the Lutsk and Khmelnitsky - where the national symbols would normally be visible.

"It appears the Russians have taken the flags down at both ships but not put out their own," Seleznyov said.

More than 14,500 people serve in the Ukrainian navy, accodring to the country's Defence Ministry website, with most of them stationed in Crimea. (Reporting by Aleksandar Vasovic; Writing by Gabriela Baczynska; Editing by Andrew Roche)

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