BAGHDAD (AP) – Four members of an Iranian-backed Shiite cell confessed to bombing a public market in central Baghdad, a U.S. spokesman said Saturday. He also blamed Shiites for recent attacks on U.S. bases, raising fears that a three-month truce by the most feared Shiite militia may be at an end.

The blast 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 decline in the bombings and shootings that once rattled the Iraqi capital daily.

During overnight raids, U.S. and Iraqi soldiers arrested four members of an unidentified Shiite “special groups cell,” who confessed to the bombing, U.S. spokesman Rear Adm. Gregory Smith told reporters.

“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-Qaida in Iraq so residents would turn to Shiite militias for protection.

He said Shiite “special groups” were believed responsible for rocket and mortar attacks against American 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 U.S.-protected area in weeks. U.S. officials said the barrage wounded an undisclosed number of people but caused no deaths.

Baghdad was calm Saturday, with no major incidents reported by police. But the recent uptick in attacks raised questions whether anti-American cleric Muqtada al-Sadr, head of the Mahdi Army militia, would call off the six-month truce he ordered last August.

U.S. officials have said the truce was generally holding and partly responsible for a 55 percent decline in attacks nationwide since June.

American 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 cease-fire.”

Nevertheless, U.S. and Iraqi forces have been cracking down on al-Sadr’s followers, especially in the Shiite cities of Karbala and Diwaniyah. U.S. and Iraqi officials say they are targeting “criminal elements.”

“Iraqi and coalition forces will continue to capture and kill those who choose to dishonor Muqtada’s pledge by committing these acts of indiscriminate violence against innocent Iraqis,” Smith said.

But the ongoing crackdown has enraged al-Sadr’s followers, who control 30 of the 275 seats in parliament and have emerged as a force in Iraqi politics, threatening the position of Shiite parties allied with the U.S. and the Shiite prime minister, Nouri al-Maliki.

In a statement issued Saturday in Najaf, the Sadrist movement condemned the “ugly and shameful arrests” of its supporters.

It also warned the Iraqi government to “stop aggression against innocent civilians.”

The renewed threat from Shiite extremists illustrates the complexity of the Iraq conflict.

Al-Sadr’s August truce enabled the Americans to focus their firepower on Sunni extremists such as al-Qaida in Iraq, whose fighters have been largely driven of Baghdad and surrounding areas, military officials say.

Elsewhere, Iraqi authorities clamped a daylong curfew on the northern city of Kirkuk while soldiers and police launched a major offensive against militants in the area.

Kirkuk has seen a rise in violence that authorities blame in part on insurgents who fled security crackdowns in Baghdad. Tension among the city’s Kurdish, Arab and Turkomen population is running high because of Kurdish aspirations to incorporate Kirkuk into their semiautonomous zone.

AP-ES-11-24-07 1721EST

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