DONETSK, Ukraine — Armed pro-Russian separatists have reportedly seized a police headquarters in the eastern Ukrainian town of Konstantinovka.According to the Ukrainian press, dozens of uniformed and masked people occupied a floor at the police headquarters in the early hours on Monday and blocked the building's entrance and exit.Interior Ministry spokeswoman Laryssa Volkova said: "About 30 separatists came to the local police headquarters and occupied the ground floor.""Negotiations are under way with the local police chief. We do not know what their demands are."