DONETSK, Ukraine (AP) — Ukrainian officials say an unnamed "radical" group is keeping 60 people hostage inside a government office in the eastern city of Luhansk.

The Ukrainian Security Service said Tuesday that "separatists" have the hostages inside a security service branch in Luhansk and are threatening them with arms and explosives.

There was no word on the identities of the hostages. Ukraine says the building was seized Sunday by armed pro-Russian protesters.

Ukrainian authorities regained control Tuesday over another government building in Kharkiv, the country's second-largest city, evicting the pro-Russian protesters and detaining dozens.