KIEV, May 5 (Xinhua) -- At least eight Ukrainian soldiers were injured during a fresh "anti-terror" operation to retake Slavyansk, and a death count was still going on, Ukrainian Interior Minister Arsen Avakov said on Monday.
Avakov released the information at a briefing in Slavyansk, an eastern city of the country which has been controlled by pro-Russian activists since mid-April.
Meanwhile, local media have also reported casualties on the side of the pro-Russian activists.
A video footage posted on local social media appeared to show a gas station had exploded on a road linking Slavyansk and Donetsk in the village of Semenovka, but no casualties in the blast have been confirmed yet.
Earlier in the day, the Ukrainian Defense Ministry said in a statement that a Ukrainian military pilot had been released from hostage in Slavyansk.
On Sunday, thousands of anti-government protesters stormed the police headquarters in Ukraine's southern port city of Odessa and freed dozens of their jailed allies.
The violence happened after Friday's deadly clashes between pro- and anti-government protesters that killed at least 43 people and injured 174 others in the city.
The Ukrainian authorities launched their "anti-terror" operation to try to dislodge pro-Russian activists who are seeking closer ties with Moscow.
The activists have so far seized a number of government buildings in towns in eastern Ukraine.
Kiev has repeatedly blamed Moscow for inciting unrest and splitting Ukraine. Russia have denied all the charges.