Four prisoners and a guard were killed in clashes at a prison in the central Iraqi city of Hilla, during which eight inmates escaped, officials said on Saturday.
The clashes, in which nine people were also wounded, broke out after a prisoner seized a rifle from a guard and killed him, said Mohammed Ali al-Massudi, the governor of Babil province, of which Hilla is the capital.
"It seems this operation was organised with the help of other groups who helped the prisoners and were waiting for them outside the prison," Massudi told a news conference in Hilla, 95 kilometres (60 miles) south of Baghdad.
Prisoners also set fire to areas of the prison, he said.
"The prisoners who escaped are senior members of Al-Qaeda and Shiite militias," said Haidar al-Zambur, a member of the provincial council security committee, adding "they were all sentenced to death."
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Two silenced pistols were found on the inmates, he said, adding the incident was under investigation.
A justice ministry spokesman said earlier the clashes occurred on Friday night, and put the initial toll at three dead, while a first lieutenant in the Hilla police had said 15 inmates escaped, of whom three were later apprehended.
Zambur said this was the third attempted jailbreak from the prison.
The first was in 2006, when about 50 members of the Mahdi Army, radical anti-US Shiite cleric Moqtada al-Sadr's now-deactivated militia, managed to escape.
Prisoners also launched an unsuccessful escape attempt last April, he said.
Jailbreaks and prison unrest are relatively common in Iraq.
Six Iraqi police and 11 inmates were killed in a Baghdad jail mutiny in May, while 12 suspected Al-Qaeda members escaped from prison in the southern city of Basra in mid-January. At least two of the Basra escapees have been recaptured.