Russian troops have forced their way into a Ukrainian airbase in Crimea with armoured vehicles, automatic fire and stun grenades, while a group of pro-Russian protesters have stormed another base in the west of the region.
Reports say at least one person was injured during the assault on Belbek base, near Sevastopol.
Two armoured personnel carriers burst through the wall of Belbek base followed by Russian troops firing weapons in the air, the BBC reports. An ambulance was then seen entering the base amid reports that at least one person was injured.
The storming followed an ultimatum by Russian forces surrounding the base to surrender. The base is now said to be under Russian control.
Earlier, several hundred unarmed protesters seized a Ukrainian naval base at Novofedorivka, western Crimea. Ukrainian servicemen had barricaded themselves inside and threw smoke bombs from the roof.
Pro-Russian militia have also been seizing Ukrainian navy ships, and, backed by Russian forces, have already seized a number of Ukrainian bases in the southern peninsula.
Russian troops have taken over control of Crimea following last month's overthrow of Ukrainian President Viktor Yanukovych after mass street protests.
Ukraine and the West have condemned as "illegal" the 16 March referendum in Crimea, where voters backed a proposal to re-join Russia.
Russian President Vladimir Putin has since signed a law formalising Crimea's takeover.