A homicide bomber blew himself up inside a funeral tent in a predominantly Sunni village, killing at least 14 and wounding 17, in the third such bombing in Sunni areas in as many days.

There were no immediate claims of responsibility, but the attack bore the hallmarks of Al Qaeda in Iraq, which has been trying to derail a movement that has seen Sunnis join forces with the U.S. against the terror network.

The attacker detonated his explosives belt amid mourners in the Hajaj village on the outskirts of Tikrit, Saddam Hussein's hometown some 80 miles north of Baghdad, a police officer said, speaking on condition of anonymity because of security concerns.

The blast brought down the tent and the casualty toll rose to at least 14 killed and 17 wounded as victims were pulled from the rubble.

"I heard a big explosion and I ran away out of fear. I came back to the tent after hearing the voices of wounded begging for help," said Awad Jassim, a 25-year-old who had been making coffee over an open fire. "The tent fell down and there was chaos everywhere, but we managed to carry out the dead and the wounded."

Police, meanwhile, rounded up clansmen in Anbar province as a U.S.-backed tribal leader suggested a teenager who carried out a homicide bombing against the anti-Al Qaeda fighters had help from inside the group.

Sunday's homicide attack near Fallujah killed six people in the former insurgent stronghold and raised concerns about the infiltration of Sunni groups that have joined forces with the Americans against Al Qaeda in Iraq.

The attacker was a teenage relative carrying a box of candy at a gathering of tribal members to celebrate the recent release of a relative, Hadi Hussein, who had been released after more than a week in U.S. custody. Hussein and five other people were killed in the blast.

The young man blew himself up in a reception area as Hussein was greeting well-wishers in the compound of Aeifan al-Issawi, a leading member of the Anbar Awakening Council. Al-Issawi said he believed he was the target but the bomber got nervous and detonated his explosives before he arrived.

"I was the target," al-Issawi said. "This is not the first time that we have been targeted by our relatives who live in the same area around us."

Al-Issawi said the bomber was Ali Hussein Allawi, the 15-year-old son of an Al Qaeda militant who had traveled to the area from Samarra to visit relatives.

The tribal leader said some two dozen suspects had been rounded up and five remained detained after the attack.

He also said police were investigating how Allawi had been armed, suggesting he must have received the explosives after arriving in the area to penetrate tight security and avoid extensive checkpoints along the way.

"After the explosion, police forces detained uncles and relatives of this boy," al-Issawi said. "It is unbelievable that he came from Samarra with an explosive belt on him."

The implication that it was an inside job reflects the tangled relationships of tribes in Anbar province, a vast desert area that has been relatively calm in recent months as Sunnis switched sides to join forces with the U.S. against Al Qaeda in Iraq.

The so-called awakening movements have spread to other areas and have been hailed by the U.S. military as one of the main reasons for a recent decline in violence. But the military has acknowledged concerns that some members could retain allegiances to Al Qaeda.

Rear Adm. Gregory Smith, a U.S. military spokesman, said members were carefully screened and must pledge to renounce violence before being accepted.

"That's not to say that Al Qaeda has not found a way to infiltrate some members, some groups, that clearly could be the case," Smith said Sunday, referring to the Sunni movements.

The U.S. military also said a Marine was killed Saturday during fighting in Anbar, the first U.S. combat death in the province since Oct. 8.

South of Baghdad, a roadside bomb killed another soldier in the rural Al Qaeda in Iraq stronghold of Arab Jabour on Saturday, the military said separately.

In the capital, hundreds of men carried a huge Iraqi flag as they followed the coffin of Jawad Abdul-Kadim during a funeral service in the Amil neighborhood. Protesters said he was not affiliated with any militant groups.

The military said the slain extremist brigade commander led a network of 10 groups in Baghdad that were implicated in murder, kidnappings and other criminal activity against Iraqi security forces and civilians. The suspect had established a group to collect information used to target Iraqi troops, according to the statement.

"Credible intelligence indicates he and his group are responsible for the sectarian murder of several hundred Iraqi civilians in the past year," the statement said.

The man, who was not identified by the military, ran into another room after the assault force entered the building, according to the military's account. He was killed after troops forced the door open and saw him trying to grab a weapon, it said.

U.S.-led forces have routinely carried out raids in Baghdad searching for Shiite extremists since they launched a security crackdown in the capital nearly a year ago. Residents frequently complain of unnecessarily heavy-handed behavior at the hands of the troops.

Abdul-Kadim's son, Hamza Jawad, said his father was trying to keep the troops out of the bedroom until his wife could dress properly, but one of the soldiers reached through a space in the door and opened fire.

"My father is innocent, and he is not affiliated with any group," the 13-year-old said.