Russian President Vladimir Putin attends a news conference with Turkish President Tayyip Erdogan (not seen) following their meeting in St. Petersburg, Russia, August 9, 2016. REUTERS/Sergei Karpukhin

MOSCOW (Reuters) - Russia has deployed its advanced S-400 air defense missile system to annexed Crimea, Russian news agencies reported on Friday, citing a statement from the Russian Defence Ministry.

The announcement comes two days after President Vladimir Putin promised to take counter-measures after what he said were clashes between Russian forces and Ukrainian saboteurs in northern Crimea.

Ukraine denies the clashes took place. Russia annexed Crimea from Ukraine in 2014.