Hundreds of convicts, including senior members of al-Qaeda, have broken out of Iraq's Abu Ghraib jail after comrades launched a military-style assault to free them.
Suicide bombers drove cars packed with explosives to the gates of the prison on the outskirts of Baghdad last night.
They forced their way into the compound, while gunmen attacked guards with mortars and rocket-propelled grenades.
Other militants took up positions near the main road, fighting off security reinforcements sent from Baghdad as several militants wearing suicide vests entered the prison on foot to help free the inmates.
Ten policemen and four militants were killed in the ensuing clashes, which continued until this morning, when military helicopters arrived, helping to regain control.
By that time, hundreds of inmates had succeeded in fleeing Abu Ghraib, the prison made notorious a decade ago by photographs showing abuse of prisoners by US soldiers.
"The number of escaped inmates has reached 500, most of them were convicted senior members of al-Qaeda and had received death sentences," Hakim Al-Zamili, a senior member of the security and defence committee in parliament, said.
"The security forces arrested some of them, but the rest are still free."
One security official told Reuters on condition of anonymity: "It's obviously a terrorist attack carried out by al-Qaeda to free convicted terrorists with al-Qaeda."
A simultaneous attack on another prison, in Taji, around 20km north of Baghdad, followed a similar pattern, but guards managed to prevent any inmates escaping. Sixteen soldiers and six militants were killed.
Sunni insurgents, including the al-Qaeda-affiliated Islamic State of Iraq, have been regaining strength in recent months and striking on an almost daily basis against Shia Muslims and security forces amongst other targets.
Separately, in the northern city of Mosul, 390 km (240 miles) north of Baghdad, a suicide bomber detonated a vehicle packed with explosives behind a military convoy in the eastern Kokchali district, killing at least 22 soldiers and three passers-by, police said.
A separate attack in western Mosul killed four policemen, police said.
Nearly 600 people have been killed in militant attacks across Iraq so far this month, according to violence monitoring group Iraq Body Count.