SLAVYANSK, May 02. /ITAR-TASS/. Ukrainian Air Force combat helicopters are in the sky above the east Ukrainian city of Slavyansk, the city is fully blocked, fighting is underway, a representative of the militia told Itar-Tass by phone on Friday.

He said that he has no confirmed information on those injured or killed.

Earlier, the representative said the Ukrainian authorities were conducting a full-scale sweep operation in Slavyansk, using aircraft and landing troops against civilians. The operation “started at 5 a.m., as they [Kiev leaders] pledged”.

“Armored vehicles are securing the assault by landing troops,” the militiaman said. He said he is at a checkpoint in the city center.

Massive protests against the new Ukrainian authorities, who were propelled to power in Kiev amid riots during a coup in Ukraine in February, erupted in Ukraine’s Russian-speaking southeastern regions in March after Crimea's incorporation by Russia. Demonstrators, who are demanding referendums on the country’s federalization, seized some government buildings.

The Kiev authorities have been conducting an antiterrorism operation in eastern Ukraine. Russia, which does not recognize the de facto Ukrainian leaders brought to power by the coup, has condemned the operation, apparently aimed to crack down on Ukrainian nationals supporting federalization.

Crimea's urge to reunify with Russia was caused by the republic's refusal to accept the new Kiev authorities. In a March 16 referendum, Crimeans overwhelmingly voted to secede from Ukraine and accede to Russia. The reunification deal with Moscow was signed March 18.

In the Soviet Union, Crimea used to be part of Russia until 1954, when it was gifted to Ukraine by Soviet Communist Party leader Nikita Khrushchev.