Ukraine’s Foreign Ministry has summoned Russia’s acting envoy in Kyiv for consultations following the seizure of the regional government and parliament buildings in Crimea.
Around 120 heavily armed men stormed the buildings in Simferopol earlier.
The scene was the site of Wednesday’s scuffles between Tatar groups and pro-Russian supporters.
Local Tatar leader Refat Chubarov posted that the buildings have been occupied by men in uniforms bearing “no recognisable insignia.”
Kyiv says it would regard any movements by Russian military in Crimea outside Moscow’s Black Sea Base in Sevastopol as an act of aggression.
Following the fall of President Viktor Yanukovych divisions in Ukraine have come to the fore.