Updated

A car bomb killed at least seven children and 11 other people in a northern city, providing a reminder that militants still can cause casualties despite security improvements that led U.S. troops to return a southern province to Iraqi control Wednesday.

Ninety people also were injured in the blast at a popular outdoor market in Tal Afar, said a police official, who insisted on anonymity because he was not authorized to speak to the media.

The city, a one-time stronghold of Sunni insurgents 260 miles northwest of Baghdad, was targeted in offensives by U.S. and Iraqi troops that prompted American leaders to describe it as a success story in the effort to stabilize Iraq. But sporadic attacks continue.

Also in the north, a car bomb killed two civilians in Mosul, police reported. The two attacks came a day after homicide bombers killed at least 28 people in Baqouba, northeast of Baghdad.

South of Baghdad, the formal transfer in the Qadisiyah province reflected a drop in violence and instability across Iraq and marked another success for Iraq's increasingly assertive government, which seeks a timeline from the United States for the withdrawal of American forces.

Qadisiyah, a mostly Shiite region, was the 10th of Iraq's 18 provinces to return to Iraqi authority, with U.S. and Polish troops relinquishing control at a military ceremony.

"This is further evidence of our goal to have security control in the whole of Iraq by the end of 2008," said Mouwafak al-Rubaie, Iraq's national security adviser.

In a statement, U.S. Ambassador Ryan C. Crocker and Gen. David H. Petraeus, commander of U.S. forces in Iraq, said Iraqi security forces in Qadisiyah had been operating "independently" the last two months.

"We will assist as requested," the statement said, adding that Iraqi provincial and military leadership would have to create long-term security that can lead to economic development.

In Washington, the chairman of the U.S. Joint Chiefs of Staff said he expected to be able to recommend further American troop reductions in Iraq later this year if security continues to improve.

"I won't go so far as to say that progress in Iraq from a military perspective has reached a tipping point or is reversible — it has not, and it is not," Adm. Mike Mullen said. "But security is unquestionably and remarkably better."

Qadisiyah had been the scene of fighting among Shiite factions, and U.S. and Iraqi troops conducted a big operation there last year. The handover was delayed from last month.

U.S. forces also have delayed the handover of Anbar province, the sprawling region west of Baghdad where occasional bombings and combat occur despite a sharp drop in violence. Anbar had been a stronghold of Al Qaeda in Iraq and other extremist groups until Sunni tribes turned on them and allied with the United States.

Diyala province, northeast of Baghdad, is another trouble spot. On Tuesday, two homicide bombers killed 28 people in a crowd of army recruits outside a military base in Baqouba. Iraq has said it will soon launch an offensive in Diyala against militants who are trying to regroup, and U.S. commanders say they will assist.

In Baghdad, a female homicide bomber blew herself up Tuesday evening inside the house of a municipal leader who was planning to establish a U.S.-allied Sunni group, an official connected with the group reported Wednesday.

Saad Awad, the leader in the Abu Ghraib district, escaped unharmed but his father was among three men killed while seven others were injured, said the official, who did not want to be quoted by name out of concern for his safety.

The U.S. military confirmed the attack.

The Iraqi Red Crescent Society, meanwhile, said Wednesday that its chief and two deputies have been summoned by an investigative court that is probing alleged corruption.

Adnan al-Kadhimi, one of the deputies sought for questioning, said Red Crescent chief Saeed Haqi was out of the country on official business and heading for the United States. Al-Kadhimi said the agency was preparing a legal defense.

Iraq's Red Crescent group plays a major role in aid operations throughout the country.