Story highlights The claims are made on an al Qaeda website

There are fears of a return of sectarian bloodshed in Iraq

A string of explosions killed dozens of people last week

Violence and political turmoil erupted just days after U.S. troops withdrew

Al Qaeda in Iraq claimed responsibility Tuesday for a string of attacks that killed almost 70 people and wounded more than 200.

The seemingly coordinated explosions Thursday struck during the height of morning rush hour, hitting a number of Baghdad's primarily mixed Sunni-Shiite neighborhoods. Nine car bombs, six roadside bombs and a mortar round all went off in a two-hour period, targeting residential, commercial and government districts in the Iraqi capital, police said.

"The series of special invasions launched, under the guidance of the Ministry of War in the Islamic State of Iraq, to support the weak Sunnis in the prisons of the apostates and to retaliate for the captives who were executed," the group said on an al Qaeda website.

Iraq's leadership is dominated by Shiite Muslims, including Prime Minister Nuri al-Maliki. The country's Sunni minority held power under former leader Saddam Hussein.

A recent political crisis has raised fears of a return of the sectarian bloodshed in Iraq that ripped the country apart at the height of the war a few years back.

JUST WATCHED Bloodshed in Baghdad Replay More Videos ... MUST WATCH Bloodshed in Baghdad 03:50

JUST WATCHED Iraq's future hinges on political crisis Replay More Videos ... MUST WATCH Iraq's future hinges on political crisis 02:41

JUST WATCHED Iraq after the withdrawal Replay More Videos ... MUST WATCH Iraq after the withdrawal 04:40

On December 19, al-Maliki, a Shiite, ordered the arrest of the Sunni vice president, a move that escalated sectarian tensions and threatened to collapse Iraq's fragile power-sharing government.

The political turmoil as well as the recent spate of violence erupted just days after the final U.S. troops withdrew.

Violence in Iraq has declined in recent years but last week's attacks were among the worst since August when a series of coordinated bombings killed at least 75 people in 17 Iraqi cities.