Iraqi militants stormed two prisons, including the notorious Abu Ghraib, sparking clashes that killed 41 people and freeing at least 500 inmates, officials said on Monday.
The coordinated attacks on Taji prison, north of Baghdad, and Abu Ghraib, west of the capital, were launched on Sunday night and raged for around 10 hours, officials said.
Abu Ghraib prison, already infamous as a center for the torture of opponents of now executed dictator Saddam Hussein's regime, gained new notoriety under the US-led occupation when graphic pictures emerged of the abuse of prisoners.
"About 500 prisoners escaped from Abu Ghraib prison," Hakem al-Zamili, a member of the parliamentary security and defence committe, told AFP. The official said most of them were convicted senior members of Al Qaeda who had received death sentences.
Zamili said that, to his knowledge, no inmates escaped from the prison in Taji.
But MP Shwan Taha, also a security and defence committee member, said in an online statement that between 500 and 1,000 inmates escaped from the two prisons.
Officials said at least 20 members of the security forces were killed and 40 wounded in the attacks.
And the justice ministry's spokesman said that 21 inmates were killed and 25 wounded during rioting at the prisons.
It was not immediately clear how many of the militants who attacked the prison were killed, wounded or captured.
The attacks were launched at around 9:30 pm (1830 GMT) on Sunday when the militants fired mortar rounds at the prisons.
Four car bombs were detonated near the entrances to the jails, while three suicide bombers attacked Taji prison, a police colonel said.
Five roadside bombs also exploded near the prison in Taji.
Fighting continued throughout the night as the military deployed aircraft and sent in reinforcements around the two facilities.
The situation was eventually brought under control on Monday morning, according to the colonel.
"The security forces in the Baghdad Operations Command, with the assistance of military aircraft, managed to foil an armed attack launched by unknown gunmen against... Taji and Abu Ghraib," the interior ministry said.
"The security forces forced the attackers to flee, and these forces are still pursuing the terrorist forces and exerting full control over the two regions," it added.
But comments posted on social media, including some Twitter accounts apparently operated by jihadists, said thousands of prisoners had escaped.
The attacks on the prisons came a year after Al Qaeda's Iraqi front group announced it would target the Iraqi justice system.
"The first priority in this is releasing Muslim prisoners everywhere, and chasing and eliminating judges and investigators and their guards," said an audio message attributed to the group's leader, Abu Bakr al-Baghdadi, in July last year.
Prisons in Iraq have previously been hit by escape attempts, uprisings and other unrest.
Abu Ghraib won new notoriety in 2004 when photographs were published showing Iraqi detainees being humiliated and abused by their US guards in a massive blow to the image of the US-led occupation.
Deadly violence also hit security forces in northern Iraq on Monday.
A suicide bomber blew up a vehicle near an army patrol in the city of Mosul, killing 12 people and wounding 16, while a roadside bomb wounded five people, among them three police.
And two roadside bombs near Mosul killed a soldier and wounded another and a civilian.
Iraq has faced years of attacks by militants, but analysts say widespread discontent among members of its Sunni Arab minority, which the government has failed to address, has fuelled a fresh upsurge in unrest.
With the latest attacks, nearly 600 people have been killed in violence so far this month and more than 2,800 since the beginning of the year, according to AFP figures based on security and medical sources.