Kostyantynivka, with a population of 80,000, is strategically located between Donetsk, where militants have declared a “people’s republic”, and the separatist stronghold of Slovyansk. A Ukraine interior ministry spokesman said: “At 6am, about 30 separatists came to the local police headquarters and occupied the ground floor. Negotiations are under way with the police chief. We do not know what their demands are.”