Ukrainian government forces police the town hall in the eastern city of Mariupol.

They reportedly retook the occupied building from armed pro-Russian separatists over night.

It was one of several clashes on Thursday, as the government closes in on separatist military strongholds in the east.

One protester says he was inside the building when it was stormed during the night.

(SOUNDBITE) (Russian) UNIDENTIFIED MAN WITH WOUND TO HIS HEAD, CLAIMING TO BE PRO-RUSSIAN ACTIVIST ESCAPED FROM TOWN HALL, SAYING:

"Unknown men in masks with no signs, shouting, attacked us. They were beating everybody in sight, indiscriminately. Then they gathered everybody in one room. When asked to provide medical assistance, they refused."

Burning car tires at a rebel checkpoint in Slaviansk, the new epicenter of the separatist movement.

Government forces took control of three security checkpoints here on Thursday, killing up to five pro-Russian rebels.

But within