The number of daily attacks in Mosul has dropped at least 85 percent since U.S.-Iraqi forces began an offensive against Sunni insurgents in the city earlier this month, the top U.S. commander in northern Iraq said Wednesday.

Maj. Gen. Mark Hertling said U.S. and Iraqi forces had not met fierce resistance since the operation began on May 10, largely due to the large numbers of troops on the street, an initial curfew and extensive preparations and construction of new checkpoints.

But he warned that was likely to change as the extremists try to regroup.

"We anticipate there will be some attacks by the enemy once they come out of this initial phase of being surprised within the city," he told reporters during a news conference in Baghdad. "We anticipate that there might be car bombs, suicide vests or things like that."

The U.S.-Iraqi crackdown that began May 10 in Mosul, which the military has dubbed the last urban stronghold of al-Qaida in Iraq, is the latest bid by Prime Minister Nouri al-Maliki to contain rampant violence in Iraq. The other two in the southern city of Basra and Baghdad's Sadr City district focused on Shiite extremists.

Hertling said 1,200 suspected militants have been captured in the offensive, with some 200 believed to be members of "terrorist organizations," adding his forces were monitoring some 13 insurgent groups.

He said much of the city of 1.9 million people was under control, although three unspecified neighborhoods remain volatile. Attacks in the city have dropped from an average of about 40 per day in the week before the operation began to the current figure of four or six per day, he said.

"I'm very happy with what's going on there," he said. "We are in pursuit of these criminals and terrorists and there could be dangers any day so the people still have to be careful."

Hertling also said the military has detected an increasing use of female suicide bombers in northern Iraq.

Underscoring the threat, two women bombers blew themselves up near an office of a U.S.-allied Sunni group, killing one person and wounding 16 on Saturday northeast of Baghdad.

Hertling acknowledged that women laden with explosives often are more easily able to evade detection as men are reluctant to search them. He said there was a critical need to train more women as police, adding that 112 women recently entered the Kirkuk police academy.

"There is a demand for more female security officers, both in the police and private security firms. There is a tendency to allow women to go through checkpoints without searching them as closely," he said.

He also said most of the suicide attacks were occurring outside urban areas where security is not as tight.