KIEV, May 6 -- Dozens of people were killed as Ukrainian forces battled pro-Russia activists in the country's eastern city of Slavyansk on Monday, Interior Minister Arsen Avakov said Tuesday.

"According to our estimates, some 30 pro-Russia insurgents were killed," Avakov wrote on his Facebook page.

On Monday, the Ukrainian Interior Ministry said at least four Ukrainian servicemen were killed and some 30 more wounded during the raid in Slavyansk.

The Ukrainian authorities launched an "anti-terror" operation in the city to try to dislodge pro-Russia activists who are seeking closer ties with Moscow.

The activists have seized a number of government buildings in towns in the eastern part of the country.

Kiev has repeatedly blamed Moscow for inciting unrest and splitting Ukraine, but Russia has denied all the charges.