Russian servicemen near Belbek military base in the Crimea REUTERS/Vasily Fedosenko

Russian Special Forces have overwhelmed the final military base in the Crimean peninsula still occupied by Ukrainian forces, just hours after the base's commander ordered his soldiers to stand their ground. Colonel Yuli Mamchur, who commanded the Belbek Airbase near Sevastopol, had earlier met Russian officials who demanded his surrender.

As Russian troops, plus balaclava-clad militia and men wearing Cossack-style hats, encircled the base, Mamchur refused to surrender, telling his heavily outnumbered troops to fire warning shots over the heads of the Russians if necessary – the first Crimea-based Ukrainian commander to resist.

However, shortly after the deadline expired for the Ukrainians to leave, Russian troops took the base by force using armoured vehicles and blast bombs, rounding up the Ukrainian troops to a parade ground inside. One person is reported shot, though their condition is not yet known. Commander Mamchur is now in Russian custody.

Crimea's new authorities have invited Ukrainian forces to join them but have also seized some ships and bases by force. Some Ukrainian troops have withdrawn to the mainland since Russia's formal annexation took place last week –a move widely condemned by the international community.

Up the coast from Belbek, pro-Russian demonstrators have stormed and occupied Novofedorivka naval base, tearing down Ukrainian emblems. The Ukrainians threw smoke canisters but the crowd entered the building, all Ukrainian forces eventually leaving.

100 monitors from the Organisation for Security and Co-operation in Europe (OSCE) will soon arrive in the region to gauge the political and security situation. Russia agreed to the move but has refused to allow the monitors entry into Crimea.

In a statement Russia's Foreign Ministry said: "The mission's mandate reflects the new political and legal realities and does not apply to Crimea and Sevastopol, which became a part of Russia. Russia hopes that the objective and impartial work of the international observers will help to overcome the internal Ukrainian crisis, stop rampant nationalist banditry, eradicate ultra-radical tendencies."