According to the Russian Baza Telegram channel, which is linked to security forces, several people seized a colony, taking about four hostages, three of whom were killed, including a Federal Penitentiary Service employee.
Two people escaped — one employee and one prisoner — who were hospitalized with cuts and wounds. The head of the colony, Andriy Devyatov, is in intensive care after being captured.
The attackers initially claimed affiliation with the Islamic State, though this is still being verified.
Sources say the attackers are demanding $2 million and a helicopter.
On June 16, prisoners also took hostages at Rostov-on-Don pretrial detention center No. 1, where Ukrainian political prisoners are held.
The Federal Penitentiary Service reported killing six participants in that incident.