A female homicide bomber struck Sunday in a predominantly Shiite area of central Baghdad, killing at least three people in an attack that occurred as Iraqi officials have been stressing the capital's increased security.

Police in the Masbah commercial area said they thought the woman was suspicious and asked her to stop. The woman, who wore a black Islamic robe, fled to a nearby building and the explosives detonated, said an officer who spoke on condition of anonymity because he was not authorized to release information.

With the anniversary this week of the so-called surge of U.S. troops that aimed to clear insurgent forces from Baghdad and surrounding areas, Iraqi authorities have been emphasizing the security gains achieved since then.

After a sharp initial spike in military and civilian casualties, overall violence has declined dramatically, particularly in Baghdad, although U.S. military commanders have been careful to stress that al-Qaida remains a serious threat.

Iraqi Prime Minister Nouri al-Maliki hailed the "victory in Baghdad" Friday, while the top Iraqi commander for the capital, Lt. Gen. Abboud Qanbar, said Saturday that the daily toll of bullet-ridden bodies found in the city has dropped to about four — down from at least 43 — under the crackdown.

Defense Minister Abdul-Qader al-Obeidi said that the buildup of U.S. troops has helped secure most of Baghdad. But challenges remain from al-Qaida in northern Iraq, and what he called "criminals, gangs and smugglers" in the south, where Shiite militias are struggling for control of the oil-rich area.

"There is 90 percent security in the capital," al-Obeidi told The Associated Press on the sidelines of a meeting in Dubai, United Arab Emirates.

The top U.N. authority for refugees gave Baghdad a vote of confidence Saturday by announcing that he would send a new representative to work in the city, and would increase his staff here from two people to five.

The U.N. and many other aid agencies moved from Baghdad to Amman, Jordan, after devastating attacks, including the truck bombing of the world body's Iraq headquarters in August 2003 that killed 22 people including the top U.N. envoy in Iraq, Sergio Vieira de Mello.

"We have confidence in the future of Iraq," U.N. High Commissioner for Refugees Antonio Guterres said at a joint news conference with Iraq Foreign Minister Hoshyar Zebari.

Guterres said the new U.N. representative on the refugee crisis "will be in Baghdad and no longer in Amman as it has been the case. We believe it is here that the essential work needs to be done."

In the northern city of Mosul, a police officer and two civilians were killed when a bomb in a parked car detonated, police said. The officer was examining the car when it was exploded remotely.

Mosul is the last major urban stronghold of insurgent forces and a focus of the U.S. and Iraqi military efforts.