Eleven members of illegal armed groups have been detained in the active phase of the anti-terrorist operation in Mariupol, Ukrainian Interior Minister Arsen Avakov said.

Two land mines have been defused, he added.

"A car heading for Donetsk has been stopped at a roadblock, the car was packed with weapons," he wrote on Facebook.

The minister reported stability in the city.

The Ukrainian flag has been raised above the Mariupol City Council, Avakov said.

In his words, the operation started at 0450 on Friday.