Ukrainian police officers stand outside the regional administration building in the eastern Ukrainian city of Donetsk. REUTERS/Stringer

Donetsk, Ukraine - A loud explosion rang out in central Donetsk on Thursday evening followed by a series of smaller explosions that sounded like artillery, AFP journalists said.

The explosions were heard shortly after 10:00 pm local time (1900 GMT). A spokeswoman for the separatist Donetsk people's republic could not be immediately reached for comment.