BAGHDAD - Al-Qaeda fighters and other Sunni insurgents have largely scattered from the northern city of Mosul in the face of a U.S.-Iraqi sweep, fleeing to desert areas farther south, an Iraqi commander said yesterday. He vowed the forces would not allow them to regroup.

The U.S. military said al-Qaeda in Iraq was "off-balance and on the run" but remained a very lethal threat, tempering remarks by the U.S. ambassador a day earlier that the terror network was closer than ever to being defeated.

The comments came amid a flurry of attacks in Baghdad and other areas, most likely attributable to Sunni insurgents. A roadside bomb targeted a patrol of U.S.-allied Sunni Arab fighters near a mosque in northern Baghdad, killing one of the Awakening Council members and wounding three others, a police official said.

Bombings and shootings killed three people in and around the city of Baqubah, north of Baghdad, where U.S. forces waged a fierce offensive last year to break al-Qaeda domination of the city, police said.

Iraqi security forces also made their first major discovery of a weapons cache in Baghdad's Shiite district of Sadr City, where troops and police deployed last week - a move that could raise tensions in the military's truce with the powerful Mahdi Army militia.

The U.S. and Iraqi military have called Mosul the last remaining urban stronghold for al-Qaeda in Iraq after successes against the terror network in Baqubah and major towns in the western province of Anbar.

Maj. Gen. Mohammed al-Askari, a spokesman for the Iraqi Defense Ministry, said security forces had arrested about 1,030 people during their sweep the past week in Mosul. Another 251 detainees had been freed after being cleared of suspicion, he said.

He said about 2,000 al-Qaeda and other Sunni insurgent fighters were believed to have been in the city before the sweep was launched. He could not say how many remained in the city but said most who managed to flee were believed to be taking refuge in deserts near the cities of Tikrit and Ramadi, further south.

"Now they are in a confused situation," he said at a joint news conference with U.S. military spokesman Rear Adm. Patrick Driscoll. "We will not allow them to reorganize themselves."

U.S. Ambassador Ryan Crocker said Saturday that Iraqi forces had made important progress in confronting extremists, adding: "You are not going to hear me say that al-Qaeda is defeated, but they've never been closer to defeat than they are now."

Driscoll sounded a cautionary note, however. He said that while al-Qaeda in Iraq fighters "certainly are off-balance and on the run," the group "remains a very lethal threat."

Still, the number of attacks in the last week decreased to a level "not seen since March 2004," he said, without giving figures.