Baghdad • An al-Qaida front group in Iraq has claimed responsibility for the wave of attacks that ripped through markets, cafes and government buildings in Baghdad on a single day last week, killing 69 people and raising new worries about the country’s path.

The coordinated attacks struck a dozen mostly Shiite neighborhoods on Thursday in the first major bloodshed since U.S. troops completed a full withdrawal this month after nearly nine years of war. They also coincided with a government crisis that has again strained ties between Iraq’s Sunnis and Shiites to the breaking point, tearing at the same fault line that nearly pushed Iraq into all-out civil war several years ago.

The claim of responsibility made no mention of the U.S. withdrawal. Instead, it focused its rage on the country’s Shiite-dominated leadership, which Sunni insurgents have battled since it came to power as a result of the U.S.-led invasion that toppled Saddam Hussein in 2003.

"The series of special invasions (was) launched ... to support the weak Sunnis in the prisons of the apostates and to retaliate for the captives who were executed," said the statement in the name of the Islamic State of Iraq.

According to the SITE Intelligence Group, a U.S.-based organization that monitors jihadist Web traffic, the claim of responsibility was posted late Monday on militant websites.

The group said the attacks were proof that they "know where and when to strike and the mujahedeen will never stand with their hands tied while the pernicious Iranian project shows its ugly face."

The remark was in reference to accusations by Sunni militants that Iraq’s Shiite-dominated government has allied itself too closely with neighboring Shiite power Iran, a bitter enemy of Iraq under the regime of Saddam Hussein.

The Baghdad military spokesman, Maj. Gen. Qassim al-Moussawi, said al-Qaida in Iraq — no longer focused on fighting U.S. forces — is hoping to take advantage of the current political tension to re-ignite sectarian warfare.