Baghdad ? A female suicide bomber killed at least 15 people, including several police officers, and wounded dozens Sunday in an attack in front of a government building in Diyala province, Iraqi and U.S. officials said.

It was the second time this year that a suicide bomber, apparently intent on killing police officers, attacked the busy downtown area of the provincial capital, Baqouba, about 35 miles northeast of Baghdad.

The explosion occurred about 12:30 p.m., according to Lt. Gen. Abdul Karim al-Robaei, the commander of the province’s security operations center. At least eight policemen, including a captain, were killed, he said.

The U.S. military said more than 45 people were wounded in the attack.

Jassim Mohammed al-Saedi, a wounded policeman, said officers were transporting prisoners to court when he heard the blast.

“We only heard the sound of a big explosion and a number of stores were set on fire,” he said in a telephone interview from Baqouba General Hospital. “Dead and injured policemen and civilians were lying in the street.”

Saedi said the area is off-limits to nonofficial vehicles. He said the attacker stepped out of a car, walked toward a group of police officers and detonated explosives strapped to her waist. Capt. Karim Abid Ali al-Saedi was among those killed, he said.

The U.S. military says female bombers have carried out at least 21 suicide attacks this year in Iraq, up from eight last year.

The most recent before Sunday’s occurred June 14, when a woman dressed in a black abaya walked into a cafe in Baqouba where soccer fans were celebrating Iraq’s victory over China.

An Iraqi police officer became suspicious about the woman and dispersed the crowd, according to the U.S. military.

“He spotted the detonator and began screaming” for the crowd to leave the area, a U.S. military spokesman said in a statement.

In April, a suicide bomber killed nearly 50 people near the site of Sunday’s bombing.