KIEV (REUTERS) - Russian navy ships have blocked off the Kerch Strait which separates Ukraine's Crimea region and Russia, the Ukrainian border guard service said on Tuesday.

The border guards have said that Russian servicemen are in control of the Crimean side of the narrow channel and that Russian armoured vehicles have been sighted on the Russian side.

"The Kerch Strait is blocked by two Russian ships - from the north and from the south," Pavel Shishurin, the deputy head of the border guards, told reporters.

The Russian military has not confirmed his comments.