MADAIN, Iraq — Hundreds of Iraqi security forces launched an operation yesterday to root out Sunni insurgents at the tip of Iraq's "Triangle of Death" but found no hostages despite reports that up to 100 Shiites may have been seized.

Iraqi forces fanned through the dusty streets of Madain and took positions on rooftops in the town south of Baghdad, while Sunni leaders dismissed the reports of a hostage crisis as a hoax.

The U.S. military, whose forces stood by in case they were needed, called the operation in Madain a significant step forward in the training of Iraqi forces, which is key to America's exit strategy in the 2-year-old war.

"The city is now under full control," interim Prime Minister Ayad Allawi's office said, adding that 10 suspected insurgents were arrested and many weapons seized.

In Baghdad, Iraq's most powerful Shiite bloc said it wants ousted leader Saddam Hussein put to death if he is convicted of war crimes. If the interim president won't sign the execution order, he should resign, an alliance spokesman said.

"This is something that cannot be discussed at all," said Ali al-Dabagh, a legislator from the Shiite clergy-led United Iraqi Alliance. "We feel he is a criminal. He is the No. 1 criminal in the world. He is a murderer."

Interim President Jalal Talabani was quoted by the British Broadcasting Corp. (BBC) yesterday as saying he likely would abstain from signing any execution order because of his opposition to the death penalty.

"I personally signed a call for ending execution throughout the world, and I'm respecting my signature," Talabani told the BBC. He conceded, however, that he probably was alone in the government in holding this view. No date has been set for Saddam's trial.

Madain is an agricultural town of about 1,000 families, evenly divided between Shiites and Sunnis, at the northern edge of a region considered to be a stronghold of the Sunni insurgency. When hundreds of police entered the town yesterday, they met no resistance and found no hostages.

On Sunday, National Security Minister Qassim Dawoud had warned parliament of attempts to draw the country into sectarian war. Yesterday, he pledged to "chase down terror everywhere" and said Iraqi forces in Madain had found mines, ammunition, bomb-making equipment and six completed car bombs.

The country's most-feared insurgent group, al-Qaida in Iraq, denied any fighters were captured in Madain, saying in a statement posted on an Islamic Web site that only unarmed Sunni civilians were detained.

Six Iraqi police and special-forces battalions, each of which typically includes about 300 troops, participated in the operation, the Interior Ministry said.

Fewer than 200 U.S. troops were on standby to help, the U.S. military said.

Lt. Col. Clifford Kent, a spokesman for the U.S. 3rd Infantry Division, said it was the first time that Iraqi forces had conducted an operation of this scale on their own. He called it a "significant step forward" for the Iraqis.

Shiite leaders and government officials initially claimed Sunni militants captured up to 100 Shiites in and around Madain last week and were threatening to kill them unless all Shiites left the area. Over the weekend, Iraqi police and military circled the town and raided suspected hideouts.

By yesterday, however, Iraqi officials had produced no hostages, and some were saying the number taken had been exaggerated for political purposes.

Madain residents; the Association of Muslim Scholars, an organization of Sunni clerics; and al-Qaida in Iraq denied any hostages had been taken. Al-Qaida in Iraq said the claim was used to justify a military attack on Madain aimed at Sunnis.