Four members of an Iranian-backed Shiite cell confessed to bombing a public market in central Baghdad, a US spokesman said. He also blamed Shiites for recent attacks on US bases, raising fears that a three-month truce by the most feared Shiite militia may be at an end.
The blast on Friday in the al-Ghazl pet market killed at least 15 people, wounded 56 and shattered a growing sense of public confidence that has emerged following a sharp decline in the bombings and shootings that once rattled the Iraqi capital daily.
During overnight raids, US and Iraqi soldiers arrested four members of an unidentified Shiite "special groups cell," who confessed to the bombing, US spokesman Rear Admiral Gregory Smith told reporters on Saturday.
"Based on subsequent confessions, forensics and other intelligence, the bombing was the work of an Iranian-backed special groups cell operating here in Baghdad," Smith said, adding that he was not accusing Iran itself of ordering the blast.
The market is located in a Shiite area and has been targeted before by Sunni extremists. But Smith said the attackers wanted people to believe that the bomb, packed with ball-bearings to maximize casualties, was the work of al-Qaeda in Iraq so that residents would turn to Shiite militias for protection.
He also said Shiite "special groups" were believed responsible for a series of rocket and mortar attacks against US bases in eastern Baghdad on Nov. 18.
In addition to those attacks, an estimated 10 rockets or mortars fired from Shiite areas slammed into the Green Zone last Thursday in the biggest attack on the US-protected area in weeks. US officials said the barrage wounded an undisclosed number of people but caused no deaths.
Baghdad was generally calm on Saturday, with no major incidents reported by police. But the recent uptick in attacks raised questions whether anti-US cleric Muqtada al-Sadr, head of the Mehdi Army militia, would call off the six-month truce he ordered in August.
US officials have said the truce was generally holding and partly responsible for a 55 percent decline in attacks nationwide since June.
US commanders have been careful not to accuse al-Sadr himself of any role in recent attacks. Smith said the market bombing "demonstrates there are individuals who continue to ignore Muqtada al-Sadr's pledge of a ceasefire."