The order came less than 24 hours after Secretary of State Condoleezza Rice flew here to appeal to Shiite leaders to reach out to Sunni Arabs, in the hope of weakening Sunni support for the insurgency. But it could complicate the battle against the rebels.

U.S. officials say some insurgent groups may be ready to turn toward peace, if they can be persuaded that Sunni Arabs can take part effectively in Iraq's nascent democracy, beginning with a full role in drafting the new constitution.

The Shiite leaders sought to give the ban on raids of mosques added impact among Sunnis by having it announced by the defense minister, Sadoun al-Dulaimi, a Sunni Arab who has been in office less than a week.

Al-Dulaimi, 51, a sociologist who fled Saddam Hussein's repression in 1990 for England, has been disparaged by Sunni intermediaries who had pressed for Cabinet posts for Sunnis with closer links to the period of Sunni minority rule that ended with Saddam's overthrow.

At a news conference in the Defense Ministry, his first public appearance, al-Dulaimi said the order extended to college campuses and Christian churches, and applied to Shiite as well as Sunni religious sites. He said raids had been "terrifying worshippers," adding, "The holy places must not be violated by the security forces, nor religious leaders arrested, and that will not happen anymore."

He said that the security agencies under Saddam had spread "terror" among Iraqis in the name of protecting Iraq, and that the new government was determined not to do the same by attacking places that Iraqis had the right to consider immune to violence. "A sense of public security cannot be achieved by spreading fear," he said.

The U.S. military command had no immediate comment on the order, which seemed likely to have a significant effect on operations in Sunni Arab areas that have been insurgent strongholds. American policy has been to attack mosques and religious schools only when they are used as firing positions, as occurred frequently, according to U.S. commanders, during the offensive that recaptured Fallujah in November.

But Iraqi troops operating under American command have raided scores of mosques in the past 18 months, arresting dozens of clerics and often carrying away large hauls of weapons and ammunition, including bomb-making equipment and antitank rockets.

During two uprisings last year led by Muqtada al-Sadr, the Shiite cleric with a wide following, raids were conducted against Shiite mosques, too, but the main targets have been Sunni.

In another sign that Shiite leaders have recognized the need to defuse tensions with Sunni Arabs, three Shiite leaders issued statements Monday denouncing the worsening sectarian violence, which has included the discovery of at least 50 execution-style slayings in recent days.

The statements came from Prime Minister Ibrahim al-Jaafari, who leads the bloc of religious Shiites who control the new government, and from al-Sadr, who has since turned, at least tentatively, toward politics.

But the most powerful call came from Grand Ayatollah Ali al-Husseini al-Sistani, the country's most revered Shiite cleric, who played a decisive role in assembling the Shiite alliance that won January's elections and whose word is regarded by many Shiites as decisive on political as well as religious issues.

Al-Sistani met on Monday at his sanctuary in Najaf with al-Jaafari, and gave the prime minister a message emphasizing the need for Shiites and Sunnis to work together on the country's future.