But an American commander in the area said he would continue to adhere to a policy of not searching mosques unless troops were fired on from them. "It's sovereign territory," said Capt. John Ives of the Third Infantry Division in Falluja, about 35 miles west of Baghdad.

Mosque members insisted that the explosion had been caused by an American missile fired from a helicopter or an airplane, a version of events that quickly gained currency on the streets of Falluja and beyond, prompting vows of revenge.

Captain Ives said that since the explosion there had been a series of incidents of men driving by and firing at American soldiers, but that none had hit their targets.

The Central Command statement said an investigation by the military and the Iraqi police had concluded that "coalition forces were in no way responsible for the explosion."

Neighbors interviewed on Tuesday concurred, saying they had heard no aircraft before the explosion but had heard that explosives were being stored at the mosque.

Another statement from the Central Command said a soldier from the Army's 352nd Civil Affairs Command had died of wounds incurred on Tuesday, when his convoy was hit by an explosive device in Baghdad.

Allied forces have carried out repeated raids trying to prevent such attacks, looking for bomb-making activity as well as weapons. But Captain Ives said American soldiers would not trespass on what he called holy ground. To do so would risk further alienating a Muslim population already seething at the American-led occupation.

Even during the investigation of the mosque explosion, which leveled two rooms adjacent to the mosque, soldiers did not enter the mosque itself, Captain Ives said. 

He added that he had received tips about guns or bomb-making activities in other mosques and had reported them to either the mayor and police chief or to a moderate, "pro-coalition" cleric who then spoke to the imam at the mosque in question.

"We tell him," he said of the moderate sheik. "He tells the imam to cease activity. It works."

In the case of Al Hassan Mosque, the only reports Captain Ives received had concerned sermons against the allied forces. He asked the moderate sheik, who could not be located today, to speak to the imam, Sheik Leith Khalil Daham.

"Unfortunately he didn't get there in time," Captain Ives said.

Sheik Daham, who died in the blast, was a young radical, just short of 25, who took over at Al Hassan Mosque just over a year ago. It is one of about 60 mosques in Falluja.

Many Sunni Muslim clerics have preached against the American occupation, but Sheik Daham's sermons, broadcast by loudspeaker, were extreme enough, and popular enough, to draw the notice of the allied forces. His best friend, Sheik Ahmad Hassan, 25, arrived today to become the new imam at Al Hassan. He said Sheik Daham had grown up poor in a village near Falluja. He left middle school in 1992 to attend a newly established religious school in Falluja. From there he went to a religious college in Baghdad.

Sheik Hassan said the young men had lived in mosques and delved deeply into the Shariah, the code of Islamic religious law, under the tutelage of an older sheik.

American concerns about Islamic militants have focused largely on Iranian-influenced Shiite hard-liners in southern Iraq. Attacks in central Iraq have generally been attributed to disgruntled former adherents of Saddam Hussein's Baath Party, which during most of its time in power followed a secular ideology.

But the use of a Sunni mosque to make bombs suggests that the resistance may have a decidedly nonsecular component. It shows, as well, how politics and self-preservation eroded Mr. Hussein's commitment to a secular Iraq. In the 1980's, Iraqis say, men were discouraged from growing beards and the Koran could not be read on television. But after the Persian Gulf war of 1991, as Mr. Hussein sought to appease the Arab world and secure his own base, he began building mosques and encouraging the teaching of the Koran.

While some restrictions on the country's oppressed Shiite majority were eased, it was the Sunni Arab minority, from whom Mr. Hussein drew most of his support, that benefited the most. Young Sunni militants from across the Muslim world thrived in Iraq, and their numbers grew during a decade of sanctions.

Sheik Hassan said he and Sheik Daham had received government stipends to study at the Islamic college in Baghdad.

"They didn't interfere in our study," he said of Mr. Hussein's officials. "They didn't interfere in our books. I have to tell you the truth."

Reaction From Bush

WASHINGTON, July 2 — President Bush today came close to taunting Iraqis who were attacking American-led forces in Iraq and said the assaults would not cause the United States to leave prematurely.

"There are some who feel like — that the conditions are such that they can attack us there," Mr. Bush said. "My answer is, bring them on. We've got the force necessary to deal with the security situation."