Al-Qaeda's Iraq franchise claimed responsibility for a wave of bombings last week that killed scores of people and heightened sectarian tensions days after the withdrawal of US troops.
The self-proclaimed "Islamic State of Iraq," inspired by the late Osama bin Laden, issued a statement Monday referring to "Thursday's Invasion" and vowing to protect Iraq's Sunni Muslims from an "Iranian project."
"With permission from Allah and his guidance, the Islamic State of Iraq knows where and when to strike," the group said in a statement posted on jihadist forums, according to the US-based SITE Intelligence Group.
"The mujahideen (holy warriors) will never stand with their hands tied while the pernicious Iranian project showed its ugly face and what it wants with Sunnis in Iraq became obvious and exposed."
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Iraq's Sunni Muslims have long viewed mostly Shiite Iran and its growing ties with Baghdad's Shiite-led government with suspicion.
The statement referred specifically to a suicide car bombing in the Karrada district of Baghdad, part of a wave of attacks on Thursday that killed 60 people and wounded nearly 200 amid a deepening political row.
The attacks were the deadliest in four months, and came days after Iraqi Prime Minister Nuri al-Maliki, a Shiite, demanded that autonomous Kurdish authorities in the country's north hand over Sunni Vice President Tareq al-Hashemi, accused of heading a death squad.
Hashemi has denied the allegations, in a crisis that threatens a coalition government that has loosely united the country's Shiites, Sunnis and Kurds following the withdrawal of US troops earlier this month.
Al-Qaeda in Iraq played a central role in the sectarian violence that gripped the country in 2006 and 2007, before Sunni tribes and militias allied with US troops -- then numbering some 170,000 -- suppressed the radical Islamist group and dramatically reduced the bloodshed.
Recent attacks -- including a suicide bombing of the interior ministry in Baghdad on Monday -- have rekindled fears of sectarian violence in the wake of the US withdrawal, carried out according to a 2008 agreement with Baghdad.