Baghdad Kirkuk

The attacks on the fourth anniversary of the war highlighted the challenges facing U.S. and Iraqi forces seeking to curb sectarian violence with a month-old security crackdown that has led to a drastic drop in execution-style killings but failed to stop the bombings.

• Visit FOXNews.com's Iraq Center for more in-depth coverage.

The afternoon blast in Baghdad shattered windows and damaged a wall of the small green-domed mosque that is situated among shops in the central Shorja market area, where a truck bomb killed 137 people last month.

Police said the blast was caused by a bomb placed in the corner behind the preacher's podium, leaving a crater in the floor. The preacher was among the 32 people wounded, police said.

Gheith Jassim, the 32-year-old owner of a textile shop near the mosque said he rushed to the mosque in a panic because he feared his brother had planned to attend prayers there. His brother had missed the prayers, but Jassim found a scene of carnage.

"When I arrived, I saw several wounded people being taken by ambulances and they were screaming from fear and injuries. There were bloodstains on the wall and some carpets were burned," he said in a telephone interview.

Jassim said some worshippers at the scene were cursing Sunni extremists and he agreed they were behind the attack as part of their effort to stoke sectarian conflict.

"We are not saved from them even during prayers. They want to ignite Sunni-Shiite strife," Jassim said.

Iraqi authorities have imposed strict security in the area to prevent car bombings that often target crowded markets.

About an hour later, four blasts occurred in a 35-minute period in different areas of Kirkuk, 180 miles north of Baghdad, killing at least 12 people and wounding more than 30.

A car bomb exploded near a market in a predominantly Arab neighborhood, killing eight people and wounding eight, police Brig. Sarhad Qadir said. A mortar shell landed on a house in the same area, wounding five civilians, he said.

A parked car packed with explosives then blew up as a police patrol passed by in a mixed Kurdish and Turkomen area in the center of the city, killing four policemen and wounding 19 people, according to Qadir, while another parked car bomb exploded near the house of an Iraqi army officer, wounding two people.

Many blame the recent increase in violence in Kirkuk on insurgents who have fled the security crackdown in Baghdad. The city, which Kurds hope to incorporate into their autonomous zone, is also the center of an ethnic power struggle.

Complete coverage is available in FOXNews.com's Iraq Center.