Al-Qaeda’s branch in Iraq asserted responsibility Tuesday for audacious raids on two high-security prisons on the outskirts of Baghdad this week that killed dozens and set free hundreds of inmates, including some of its followers.

The statement issued in the name of the Islamic State of Iraq and the Levant, the al-Qaeda affiliate in Iraq, was posted on an online extremist forum. It said months of planning went into the highly coordinated assaults on the prisons in Abu Ghraib and Taji that began late Sunday.

The attacks, among the most stunning in Iraq since a surge in violence began in April, have drawn sharp criticism from opposition lawmakers and ordinary Iraqis over the government’s efforts to keep the country safe. The increased bloodshed is intensifying fears of a return to the widespread sectarian killing that pushed the country to the brink of civil war after the 2003 U.S.-led invasion.

In its statement, al-Qaeda in Iraq dubbed the prison operation “Conquering the Tyrants” and described it as “a bold raid blessed by God” that followed several attacks that “shook the pillars of the Safavid project.”

That is a reference to what some Sunni Muslims see as undue Iranian influence over Iraq and its Shiite-led government. The Safavid dynasty, concentrated in what is today Iran, ruled stretches of the Middle East from the 1500s to the 1700s and promoted Shiite Islam as the state religion.

Al-Qaeda said the prison operation involved 12 car bombs, military-style barrages of rockets and missiles, suicide bombers and help from prisoners who had managed to obtain weapons on the inside.

Iraqi officials have said at least 25 members of the Iraqi security forces were killed in the attacks, along with at least 21 prisoners and 10 militants. Al-Qaeda boasted that its men killed more than 120 members of the security forces, and claimed that on its side, only the suicide bombers died in clashes that raged for hours.

The Interior Ministry has said several prisoners got away during the raid on Abu Ghraib, the infamous prison in Baghdad’s western suburbs that was the site of well-publicized prisoner abuse at the hands of the U.S. military after the 2003 invasion.

But several Iraqi officials, including members of parliament’s security and defense committee, have said more than 500 inmates escaped. Both prisons house thousands of inmates, including convicted al-Qaeda militants, though it appears no one broke out of the Taji prison.

— Associated Press