Baghdad ? Nearly 1,000 people have been detained in a sweep to break al-Qaida in Iraq’s sway in Iraq’s third largest city, Mosul, but many of the fighters have fled to nearby areas, where troops are hunting for them, Iraqi officials said Saturday.

Iraq’s leaders presented the crackdown as a success so far in depriving the terror network of what has been its most prominent urban stronghold since it lost hold of cities in Iraq’s western Anbar province.

But the flight of al-Qaida fighters raises the concern they can regroup elsewhere, as has often happened in the past.

Yassin Majid, an adviser to Prime Minister Nouri al-Maliki, said most of the leading insurgents had fled to the outskirts of Mosul or to a neighboring country amid the operations. He did not name the neighboring country. Mosul is about 60 miles from the Syrian and Turkish borders.

“Operations will continue and the Iraqi army will not leave Mosul until security and stability have been accomplished,” he told The Associated Press in a telephone interview.

Maj. Gen. Mark P. Hertling, the top U.S. commander in northern Iraq, whose forces are working with the Iraqi troops in the operation, said he didn’t believe significant numbers of militants had escaped.

He said Iraqi forces have surrounded the city with a circle of berms and checkpoints controlling entry and exits.

But he said some al-Qaida leaders, who directed their Mosul followers from outside the city, may have stayed away from Mosul ahead of the sweep to avoid arrest, he told The Associated Press.

“It’s been very successful,” he said. “I think the combination of the arrests plus the uncovering of a number of weapons caches will reduce the number of attacks in Mosul.”

But he warned insurgents could try to strike back in the coming days with suicide bombings in the city.

The sweep was launched Thursday, after five days of preparatory operations and arrests in the city. U.S.-backed Iraqi police and soldiers have been conducting raids on homes and have fanned out with checkpoints on city streets, though no clashes have been reported in the city, 225 miles northwest of Baghdad.

Interior Minister Jawad al-Bolani said 1,068 people have been detained over the past week, but 94 were cleared and have since been released.

Hertling said those detained included several high- and mid-level al-Qaida figures, including leaders of cells that organized suicide car bombings and facilitators for foreign fighters entering the country.