Baghdad ? Shiite politicians raged at the United States and halted negotiations on a new government Monday after a military assault killed at least 16 people in what Iraqis claim was a mosque. Fresh violence erupted in the north, with 40 killed in a suicide bombing.

The firestorm of recrimination over Sunday’s raid in northeast Baghdad will likely make it harder for Shiite politicians to keep a lid on their more angry followers as sectarian violence boils over, with at least 151 dead over the two-day period. A unity government involving Shiites, Sunnis and Kurds is a benchmark for American hopes of starting to withdraw troops this summer.

There were numerous conflicting statements from Iraqis and the Americans about the raid. Iraqi police, Shiite militia officials and major politicians have all said the structure attacked was the al-Mustafa mosque. But the U.S. military disputed this, saying no mosques were entered and that the raid targeted a building used by “insurgents responsible for kidnapping and execution activities.”

In a conference call with reporters early today, Lt. Gen. Peter Chiarelli, deputy commander in Iraq, and Maj. Gen. J.D. Thurman, commander of the 4th Infantry Division, which is in control of Baghdad, said 25 U.S. forces were in a backup role to 50 Iraqi Special Operations troops.

The mission, the generals said, was developed by the Iraqis on their intelligence that an Iraqi dental technician, kidnapped 12 hours earlier because he could not come up with $20,000, was being held in what they called an office complex.

“It’s important to remember we had an Iraqi unit with us, an Iraqi unit of 50 folks and they told us point blank that this was not a mosque,” Chiarelli said. “It’s not Mustafa mosque. Mustafa mosque is located six blocks north on our maps of this location.”

Iraqi men survey the site of a U.S. backed raid on a Shiite neighborhood in Baghdad Monday March 27, 2006 in Baghdad. At least 16 Iraqis were killed in a U.S. backed raid in a Shiite neighborhood of the capital on Sunday evening.

In an earlier statement, the military said the building had been under U.S. observation for some time.

The statement said gunmen opened fire as Iraqi special operations troops closed in. It said the troops then killed 16 insurgents and wounded three “during a house-to-house search,” detained 18 men, found a significant weapons cache and freed the hostage.

“In our observation of the place and the activities that were going on, it’s difficult for us to consider this a place of prayer,” said Lt. Col. Barry Johnson, a U.S. military spokesman.

Video from Sunday night showed male bodies with gunshot wounds on the floor of what was said by the cameraman to be the imam’s living quarters, attached to mosque itself. The compound, once used by Saddam Hussein’s government, consists of a political party office, the mosque and quarters for the imam.

The video also showed 5.56 mm shell casings scattered on the floor. U.S. forces use that caliber ammunition and have provided it to Iraqi special operations troops.

But Chiarelli said someone had gone into the scene of the raid to make it look as though there had been an assault without cause.

“After the fact someone went in and made the scene look different than it was,” Chiarelli said.

Neither general would say who might have carried out such a charade.