Russian troops in Crimea on Monday assaulted the Konstantin Olshanskiy, one of the two remaining Ukrainian naval vessels not yet surrendered to the Russian Black Sea fleet based in the peninsula's port of Sebastopol.

"They came for us," said Dimitri Kovalenko, the navy landing vessel's captain, according to the online daily Ukrainskaya Pravda, estimating the number of attackers at 200 versus his crew of 21 sailors, who abandoned ship.

Kovalenko said that shots and stun grenade blasts were heard on board the ship, which was anchored in Donuzlav Bay and could not break out for the open sea because the Russians scuttled two mothballed vessels to close off its escape route.

Meanwhile, the crew of the Ukrainian minesweeper Cherkassi, which is also anchored in Donuzlav Bay and cannot escape, repelled a boarding attempt by Russian troops by throwing explosive charges overboard to drive off the Russian - or pro-Russian - forces. Nevertheless, another boarding attempt is expected.

Interim Ukrainian President Oleksandr Turchynov on Monday ordered all Ukrainian armed forces to withdraw from Crimea after Russian or pro-Russian forces seized practically the entire Ukrainian fleet in Crimea, along with Belbek airport, military bases and several military units that had remained loyal to Kiev.

Meanwhile, the heads of state and government of the G7 group decided Monday not to allow Russia to participate in any more G8 meetings until Moscow "changes course" and the political climate becomes more acceptable for holding discussions.

The G7 members' leaders also said in a communique that Russia was being suspended from the G8 summit that was to have been held in the Russian city of Sochi - the site of the Winter Olympics - in early June.

That meeting will now be held in Brussels - according to an announcement on Twitter by European Council president Herman Van Rompuy - and will be attended by the other G7 members, namely France, the United Kingdom, Italy, Germany, the United States, Canada and Japan.

The G7, at the urging of U.S. President Barack Obama with an eye toward crafting a common Western position with regard to Russia after its move to annex Crimea, also agreed to suspend Russia's participation in other scheduled meetings.

The G7 leaders went on to reiterate that Russia had violated international norms by intending to annex Crimea after an "illegal referendum" was held in the Ukrainian peninsula and voters overwhelmingly said they wanted to rejoin Russia. EFE