Heavily armed militants have launched an audacious attack on Iraq's notorious Abu Ghraib prison, wounding 44 US troops and 12 prisoners inside.
The attack appears to have been well organised
They struck after dark, targeting an outbuilding with a car bomb and following up with another bomb, gunfire and grenades, US officials said.
According to the US military, at least 40 militants were involved.
The attack came hours before the new parliament finally elected a speaker, choosing a Sunni Muslim for the post.
Hajim al-Hassani, the current industry minister, was chosen in a secret ballot with Hussain al-Shahristani, a Shia Muslim, and Aref Taifour, a Kurd, elected as his deputy speakers.
The appointment of a Sunni is designed as a gesture to that minority which largely boycotted January's elections, having held sway over Iraq during Saddam Hussein's regime.
Sunnis have also for the most part stayed away from the country's new security forces, although senior Sunni clerics have recently urged their followers to join up.
Many of the militants fighting the new US-backed forces and targeting US soldiers are based in the Sunni community.
As parliament met, an unexplained explosion in the city sent smoke billowing into the sky.
US guards at Abu Ghraib fought the attackers for about an hour on Saturday evening, calling in helicopters and tanks to restore control.
A new explosion rattled nerves in the Iraqi capital on Sunday
At least one militant was killed and it was expected that more would be confirmed dead later, US spokesman Lt Col Guy Rudisill said.
Of the US injured, only a few had serious wounds, he added.
Some witnesses said the second car bomb had gone off while US troops were trying to evacuate the casualties from the first blast.
The jail has been targeted before with mortars.
Lt Col Rudisill said the US had had some intelligence that "something like this might happen".
"But we really don't know why this large-scale attack happened tonight," he added.
More than 3,000 detainees are held at the jail on the outskirts of the capital, Baghdad.
It was at the centre of a scandal last year over the abuse of prisoners by US guards and before that was one of Saddam Hussein's most feared jails.
The latest attack came as both US and Iraqi officials said the level of violence had gone down since January's elections.
A marine became the latest US serviceman to be killed in Iraq when he was hit by an explosion in Haditha, Anbar Province, on Saturday.