As many as 500 prisoners, most of them senior al-Qaeda members awaiting execution, reportedly escaped from Iraq's Abu Ghraib prison last night during what Reuters is calling a "military-style assault to free them."

The methods were crude but effective: Suicide bombers drove cars laden with bombs to the gates of the prison and blasted them open. Foot soldiers then attacked guards and reinforcements with explosives and guns as men in suicide vests stormed the prison to free inmates from their cells. Ten police officers and four militants were killed in the battle, which dragged on into early Monday morning. When the dust cleared, hundreds of prisoners were gone.

"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 defense committee in parliament, told Reuters.

"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 similar attack took place simultaneously at another prison in Taji, north of Baghdad, but guards were able to fight back the militants and prevent any prisoners from escaping.

Update: The Associated Press is now reporting that "dozens" were killed in the prison break, "including at least 25 members of the Iraqi security forces."

[Image via AP]