Russia has given Ukrainian forces across Crimea an ultimatum: to surrender by 4am CET on Tuesday or face a military assault.

News agency Interfax quoted a source at the Ukrainian Ministry of Defence as saying the commander of Russia’s Black Sea Fleet had issued the ultimatum.

The Ukrainian Defence Ministry has not yet confirmed this.

Putin declared at the weekend he had the right to invade Ukraine to protect Russian interests and citizens.

Russian troops and armoured vehicles have been surrounding two military bases in Crimea at Perevalnoye, 40 kilometres from the capital Simferopol since Sunday.

Ukrainian troops inside had so far refused to surrender their weapons, but say they agreed to defuse the tense situation and remove the ammunition from their guns.