MOSUL, Iraq — A suicide bomber exploded in a crowd of funeral mourners gathered outside a Shiite Muslim mosque yesterday, killing at least 47 people.

The blast, which tore through the large group packed in a tent next to Mosul's Two Sadr Martyrs Mosque, was the latest in a string of bloody attacks across Iraq that have killed at least 100 Iraqis, most of them civilians, in recent days.

Earlier yesterday in Baghdad, two police commanders were assassinated in separate ambushes and gunmen killed four cloth merchants, apparently because they sold fabric to be used for Iraqi army uniforms.

Also yesterday, police in Mosul uncovered a mass grave containing 31 bodies, adding to a grisly toll of about 40 decapitated and executed people found at two locations in Iraq on Wednesday, a senior Iraqi police official said.

The Washington Post reported that an Iraqi police general who commands a special anti-terrorism unit called al-Theeb, which means "the wolf," said police were led to the grave by a former police lieutenant, Shoqayer Fareed Sheet, who confessed on Iraqi television Wednesday night to killing 113 people.

The police commander, who because of the sensitivity of his job is publicly identified only as Gen. Abu Waleed, said the bodies were believed to be those of civilians, police officers and army soldiers who had been tortured and killed by Sheet, a Sunni Muslim, to obtain information that was turned over to Sunni insurgent groups.

The spike in violence has underscored the resiliency and nationwide reach of the insurgent campaign. The attacks come at a time of political flux, with a lame-duck Iraqi interim government and rising public frustration over protracted negotiations to form a new coalition government nearly six weeks after landmark elections on Jan. 30.

The two largest blocs, a unified Shiite Muslim slate and a Kurdish coalition, seemed close to a deal yesterday that would give them the necessary votes to form a government. But nothing had been finalized.

The Mosul attack took place during a memorial for Sayyid Hashem Araji, a prominent Shiite religious leader and imam at the mosque who had died Monday. The tent was packed with Mosul residents expressing condolences when the bomber struck around 5:30 p.m. Survivors said the explosion occurred just as dinner was about to be served, and the crowds were at their thickest.

U.S. forces have engaged in intensive efforts with the Iraqi military to root out and capture suspected insurgent leaders throughout Mosul. In a series of commando-style raids and attacks on insurgents' homes and meeting places, military commanders say, they have killed or captured hundreds of terrorists in the past several months.

"This wasn't expected, but it wasn't entirely unexpected either," said Capt. Duane Limpert, of the First Brigade, 25th Infantry Division, Stryker Brigade Combat Team. "You can have success after success after success against the insurgency, but it only takes one terrorist success to make a very big deal. They only need to get it right just once."

Mosul, a multi-ethnic city north of Baghdad, has long been a flash point for clashes between insurgents and U.S. and Iraqi forces. Last fall, insurgents routed much of the Mosul police force and established control over portions of the city.

Since then the city's neighborhoods have seesawed between insurgent and U.S. control, but U.S. forces have so far refrained from the kind of large-scale assault that inspired public outrage in Fallujah and Najaf.

A suicide attack at a dining hall on a U.S. base near Mosul in December killed 22 people, including six members of the Fort Lewis-based Stryker Brigade.

Mosul is a mix of Sunni and Shiite Arabs, ethnic Kurds and Turkmen. It was also one of the strongholds of deposed President Saddam Hussein's Baath party.

Shiites make up a majority in Iraq as a whole, but they are a minority in Mosul, which has larger populations of Sunni Arabs and ethnic Kurds. While Shiite mosques, religious celebrations and political leaders have been singled out for attack in the rest of Iraq by the predominantly Sunni insurgency, Mosul had been largely spared such attacks until now.

Shiite religious leaders, including the powerful Marjaeya religious elite headed by Grand Ayatollah Ali al-Sistani, have long appealed for patience and counseled their followers against retaliations that could spiral into a civil war. But after the Mosul bombing, some outraged Shiites issued a call to arms.

In Baghdad, meanwhile, gunmen ambushed and killed prominent police commander Lt. Col. Ahmed Abeis, chief of the Salhiya police station in central Baghdad.

He was shot along with his driver and bodyguard when insurgents opened fire on his pickup as he was heading to work around 7 a.m.

In a separate attack, gunmen killed Col. Iyad Abdul Razaq, chief of the Jisr Diyala police station in southeast Baghdad.

The state-run Iraqiya television channel announced the killing of the four cloth merchants in their shops near Baghdad's Rasheed Street market. Witnesses said the gunmen walked into the shops and opened fire.

"They say it's because they sold military clothing to the [Iraqi National Guard]," one witness told Iraqiya.

On the political front yesterday, the two largest slates in the newly elected National Assembly continued negotiations to form a government.

Members of the United Iraqi Alliance, a slate of largely Shiite Muslim candidates, and several Kurdish politicians from the Kurdish slate said the two groups had agreed that the Transitional Administrative Law, or TAL, which the Iraqi government is following now, will be the guide for future policy on some of the most contentious issues.

This is particularly important to the Kurds, who favor the policies on oil-rich Kirkuk put forth in the TAL. The TAL backs the right of return for those who were pushed out of their homes or off their land by Saddam.

But exercising that right is trickier since in many cases Arabs now live there and have put down roots themselves.

The TAL also spells out that religion will be a source of law but not the only source of law, which reassures secularists, such as the Kurds, that Iraq won't become an Islamic republic overnight.

Morin reported from Mosul and Khalil from Baghdad. Los Angeles Times staff writer Alissa J. Rubin in Baghdad and a special correspondent in Mosul contributed to this report.