BAGHDAD, (Reuters) – Iraqi police shot dead several prisoners in a shootout on Wednesday at a Baghdad military base after one prisoner grabbed a weapon from a guard and opened fire, Interior Ministry officials and police sources said.

Up to six guards were killed, one police source said, before security forces began firing into the unarmed prisoners.

There was confusion over casualty figures. Another police source and an Interior Ministry official initially said more than 20 prisoners were killed but a second official insisted there were 15 casualties in all, some only wounded, and that these included one dead guard and one wounded officer.

Later, a source at Baghdad police headquarters said it was still unclear just how many people were killed but that the first prisoner to seize a rifle had shot dead six guards.

The various accounts converged in saying that the trouble began when the prisoner grabbed a weapon from one of the guards and shot him. One Interior Ministry official said that the guard was wounded while a second prisoner also took a Kalashnikov rifle from another guard and shot him dead.

A police source said the prisoners, being held at the Adala Iraqi army base — known to U.S. forces as Camp Justice — in the northern, Shi””ite district of Kadhimiya, were on a morning recreation break when the incident began.

The first detainee to open fire managed to kill six armed guards before himself being gunned down. It was not clear how he had been able to kill so many. At least three prisoners were unaccounted for and may have escaped, the police source said.

Doctors at a nearby hospital said they had received five bodies from the camp on Wednesday morning.

Prison conditions in Iraq have been a matter of controversy.

U.S. officials have expressed disquiet since the discovery by U.S. troops last month of dozens of abused Sunni Arab suspects in a secret bunker run by the Interior Ministry, which minority Sunnis accuse of running Shi””ite sectarian militias.

The U.S. military is holding some 14,000 Iraqi guerrilla suspects and commanders say they will not transfer them to Iraqi custody until they are sure of better standards.

U.S. troops were found to have abused prisoners in 2003 at Baghdad””s notorious Abu Ghraib prison. In other incidents, U.S. troops have shot dead unarmed detainees during prison riots.