BAGHDAD (AP) – Government troops began house-to-house searches for al-Qaeda in Iraq militants in Mosul on Thursday, part of a major security operation to cleanse Iraq’s third largest city from cells of the terror network.

Prime Minister Nouri al-Maliki flew to Mosul on Wednesday to take charge of the operation by U.S.-backed Iraqi forces. Described by the U.S. military as the last major urban base of al-Qaeda in Iraq, Mosul has become the site of al-Maliki’s third security drive in two months as he attempts to defeat Shiite militants and Sunni extremists.

Al-Qaeda, however, appears to be far from defeated.

In an attack that bore the group’s hallmarks, a suicide bomber Wednesday blew himself up in a funeral tent in a village west of Baghdad, killing 22 people and wounding 40, according to police Col. Faisal al-Zubaie.

The funeral for Taha Obaid, a primary school principal killed the previous day by gunmen, was attended by local, U.S.-backed Sunni tribesmen fighting al-Qaeda militants. It was not known how many of them were among the killed and wounded.

A three-year-old son of Obaid was among those killed, said al-Zubaie.

In Baghdad, a fragile cease-fire reached this week between Shiite politicians and followers of anti-American cleric Muqtada al-Sadr in the capital’s Sadr City district came under renewed strain Thursday. Overnight and early morning clashes between U.S.-backed Iraqi forces and militiamen loyal to al-Sadr left eight men killed and 19 wounded, according to officials from two hospitals in the Shiite enclave.

The officials, speaking on condition of anonymity because they are not authorized to speak to the media, said the wounded included women and children.

Also in Baghdad on Thursday, police officials said a roadside bomb struck the convoy of the capital’s Shiite governor, Hussein Tahan, as it made its way to pick him up from his home in the central Karradah district. One of his bodyguards was killed in the blast and six others, four other bodyguards and two bystanders, were wounded.

The blast took place at 8:30 am (0530 GMT) in the central Nasr Square, according to the officials, who also spoke on condition of anonymity because they were not authorized to speak to the media.

In Mosul, the government on Thursday eased round-the-clock restrictions on movements that have been in force since May 10. Residents had been barred from leaving their neighborhoods on foot or in vehicles.

Under the latest decision, the restrictions would be in force only between 6 p.m. and 6 a.m. A total ban on motor bikes and trucks will stay in force.

There were no reported clashes during the house-to-house searches in known al-Qaeda strongholds in the western and eastern parts of the city. Al-Qaeda militants had in the past fled from areas where they expected a security crackdown and reappeared elsewhere from which they launch renewed attacks.

News of an impending anti-al-Qaeda campaign in Mosul first surfaced in January, but Iraqi forces have since erected checkpoints on major roads leading to and from the city.

Al-Maliki’s flight to Mosul, 225 miles (360 kilometers) northwest of Baghdad, is a repeat of a trip he made in late March to the southern city of Basra, where government troops fought radical Shiite militias to a standstill. That fighting later spread to Sadr City, where Mahdi Army militiamen have been fighting U.S.-backed Iraqi troops for seven weeks.

Mosul is considered the last important urban staging ground for al-Qaeda in Iraq after the terror group lost its strongholds in Baghdad and other areas in central Iraq during the U.S. troop buildup last year.

“We are closely linked with Iraqi security forces and will support operations that the prime minister is developing over the next couple of days,” U.S. military spokesman Maj. Gen. Kevin Bergner said Wednesday about the Mosul campaign.

Iraqi troops, he said, had arrested more than 500 people and captured five weapons caches. He said the operation was shifting gears.

In western Iraq, a senior U.S. commander has given fresh credence to the widely held belief that while al-Qaeda has been weakened over the past year, it remains active and capable of staging major attacks. Marine Maj. Gen. John Kelly, the commander of U.S. forces in Anbar province, said a group of al-Qaeda fighters recently infiltrated the area, went to the homes of 11 Iraqi police officers in the Anbar town of Husayba and beheaded them and one of their sons.

The insurgents crossed from the Syrian border, talked their way through a checkpoint and then went around the town grabbing police individually, he said. “I went up to the site yesterday and had never seen so much blood,” he said Wednesday at his office at Camp Fallujah west of Baghdad. “Al-Qaeda is not defeated. It’s an ideology,” he said. “Al-Qaeda is still operational but on a smaller scale.”