Security forces raided a Moscow jail and freed the warden and 14 employees several hours after they were seized Monday by inmates wearing guards' uniforms and armed with metal rods, Russian authorities said.

None of the hostages was harmed, Yuri Kalinin, the head of the agency that runs Russia's prisons and jails, told The Associated Press. He said nine women were among the captives, and that all were freed during the minute-long operation.

The hostage-takers — two prisoners sentenced to 25 years for murder and one to nine years for robbery — were demanding to be released from custody, Kalinin said.

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The uprising began when the three inmates attacked two guards during a walk on the jail grounds, donned their uniforms and seized a library at the facility in southeastern Moscow, said Alexander Sidorov, spokesman for Russia's federal penitentiary service.

Authorities initially negotiated with the hostage-takers but reportedly warned they would take other measures if the talks failed.

An explosion and what sounded like automatic weapons fire were heard hours after the first reports of the incident. Kalinin later confirmed that the blast came from a flash-bang grenade but denied that automatic weapons were fired.

First Deputy Moscow Prosecutor Vyacheslav Rosinsky said on NTV television that the inmates were armed with metal rods used to reinforce concrete.

NTV, citing unidentified officials, reported that five people had received knife wounds in the incident before the rescue operation, and the RIA-Novosti news agency later reported that two of the hostages were injured and hospitalized, also citing unidentified prison service officials.

Sidorov denied these reports, as well as an earlier RIA-Novosti report that about 40 inmates were taking part in a riot at the jail. He said there was no riot.