Ukrainian Interior Minister Arsen Avakov has announced that an antiterrorist operation is being conducted in Kharkiv, where the city center has been sealed off and local subway services have been suspended.

"Kharkiv. An antiterrorist operation has begun. The city center has been sealed off. Metro stations have also been closed. Do not worry. We will open them once we are done with it," Avakov said on his Facebook page on Tuesday morning.

He added later that the Kharkiv regional administration building had been cleared of protesters. "Some 70 separatists have been arrested," Avakov said.

The minister also claimed that "the operation was conducted without the use of firearms."

Ukraine's acting president and parliament speaker, Oleksandr Turchynov, said on April 7 that "antiterrorist measures would be taken" in relation to the separatists who seized the regional administration headquarters in the country's Luhansk, Donetsk and Kharkiv regions.