In Baghdad Friday, forces killed at least seven people and injured 30 others in an overnight assault in Sadr City, Reuters reported.
The assault focused mostly on fighters from radical cleric Muqtada al-Sadr's Mahdi Army, a Shiite militia, and led to the capture of top Shiite militia commander Abu Diraa. U.S. forces did not identify Diraa, but local witnesses pinpointed him, according to the Associated Press.
The militant leader is "an insurgent leader responsible for numerous deaths of Iraqi citizens," the U.S. military told the AP. Troops arrested him after a gunfight between Iraqi forces and insurgents in the Baghdad slum.
No Iraqi or American soldiers were killed in the raid, the military said, according to the AP.
The crackdown aims to stifle the growing violence between Shiites and minority Sunnis in Iraq.
On Friday, attacks on Sunni mosques around the country killed 10 people, according to Reuters.
In Baghdad, bombs killed five people and wounded nine following Friday prayers at two Sunni mosques.
Three people died and two were wounded in the northern part of Baghdad when a mortar attack targeted a mosque in the al-Wazeriya district.
Another two people died in a car bombing in the western al-Jihad district.
And a roadside bomb exploded outside a Sunni mosque in Baquba, about 40 miles north of Baghdad, wounding seven people.
The attacks took place despite a regular four-hour curfew on driving imposed by the Iraqi government during the period after Friday prayers. Much of the sectarian violence has targeted mosques at that time.
Meanwhile, on Thursday, the U.S. military said Iraqi and U.S. troops also arrested a second militant leader, Mahdi militia commander Adnan al-Unaybi. Troops arrested Unaybi about 60 miles south of Baghdad near Hillah, the AP reported.
Al-Sadr aide Sheik Abdul-Hadi al-Darraji denounced both raids on Thursday and Friday and said U.S. forces were responsible for the deaths of civilians.
"This is a big escalation from the American side. I condemn all the silence toward such violations and I call for the withdrawal of the American forces," al-Darraji said.
In other news Friday, Japan began pulling troops out of Iraq as part of a planned withdrawal announced by Prime Minister Junichiro Koizumi last month, Reuters reported.
About 600 troops have been stationed in the southern city of Samawah since late 2003. All 600 will withdraw over the next two weeks, the news service reported.