MOSCOW (REUTERS) - Ukraine's Interior Minister Arsen Avakov on Friday accused Russian forces of staging an "armed invasion" in Crimea, claiming they had blocked one air base and entered another airport overnight on the Black Sea peninsula.
The incidents come a day after dozens of pro-Moscow gunmen seized government buildings in the Crimean capital of Simferopol including the regional parliament, which subsequently voted to hold a referendum on May 25 to expand the region's autonomy from Kiev.
"I consider what is happening to be an armed invasion and an occupation," Mr Avakov wrote in a statement on his Facebook page.
He said that troops from Russia's Black Sea fleet - stationed in Russian-speaking Crimea - had blockaded the Belbek airfield near Sevastopol, where Ukrainian soldiers and border guards were stationed.
No armed clashes had occurred but the base was not operating as normal.
Despite not displaying any identifying insignia, the alleged Russian troops "did not hide who they belong to," Mr Avakov wrote.
He said some 120 armed men in camouflage fatigues but without insignia, whom he said also belonged to the Russian armed forces, had entered a second airport in Simferopol early on Friday.
The incidents followed the ouster of Kremlin-allied Ukraine president Viktor Yanukovych last weekend in an avalanche of change following the deaths of scores of people in clashes in Kiev.
The deposed Ukrainian president, appearing in public for the first time since he was ousted, said he spoke by telephone to Russian leader Vladimir Putin.
Ukraine's security authorities said on Friday they had regained control of two airports on the volatile Crimean peninsula that had been seized by gunmen.
There are fears that the southern region of Crimea could become a battleground between forces loyal to Ukraine and Russia.
Here are 10 things you need to know to keep up to date with the situation.
Russia's Black Sea fleet denied its forces were involved on Friday in seizing or blockading the Belbek military airport in Ukraine's Crimea region.
Russian President Vladimir Putin has ordered his government to continue talks with Ukraine on economic and trade relations and to consult foreign partners on financial aid.
Ukraine's ousted pro-Moscow president is set to hold a press conference on Friday after emerging defiant from hiding.
US Vice-President Joe Biden promised Ukraine's pro-Western interim leaders "full" US support as they seek to head off Russian influence.
The airport in Crimea's capital Simferopol was operating normally on Friday, an AFP journalist at the scene said.