Men wearing the uniform of Russia's Black Sea fleet, carrying automatic rifles, have taken up position outside a Ukrainian borderpost in the Crimean region.

It appears that the soldiers are blocking a unit of Ukrainian border guards in the Balaklava district of Sevastopol.

Russia's Black Sea fleet has a base in Sevastopol but Mosciow denies its forces have been involved in the mysterious movements across Crimea.

Armed men continued on Saturday to take over key buildings.

Here they can be seen taking up positions in the regional parliament of Crimea's capital, Simferopol.

This man is part of the group, he identifies himself as Sergei. He says he's a member of 'self-defence' militia.

(SOUNDBITE) (Russian) MEMBER OF 'SELF-DEFENCE' MILITIA, SERGEI, SAYING:

"There were no incidents near the military base here. There was an attempt by a special unit to leave the base. But they couldn't give their reasons (for leaving). We allowed units to be dispatc