BAGHDAD, Iraq (CNN) -- A female suicide car bomber attacked an Iraqi security forces checkpoint in eastern Baghdad on Sunday, killing at least three Iraqis and wounding 14, an Interior Ministry official said.
A boy walks past a burning vehicle destroyed during Sunday's clashes in Sadr City.
An Iraqi policeman and soldier were among those killed, the official added.
The bombing came as fighting in the capital's Sadr City neighborhood killed at least eight people and wounded 44 others, an official said.
The U.S. military said seven Shiite militants were killed in the overnight fighting. The seven were "special group extremists," and all but one were targeted by airstrikes, the military said.
The suicide bomber detonated her taxi near Shaab Stadium, a mostly Shiite area in eastern Baghdad, the Interior Ministry said.
Lt. Col. Steve Stover, a spokesman for the U.S. military in Baghdad, confirmed those details and said reports indicated that she triggered her explosives when she saw policemen on motorcycles. However, the U.S. military said the blast killed one Iraqi and wounded eight traffic policemen.
Suicide attacks by women are becoming more prevalent. Two female bombers struck in Diyala province on Monday and Tuesday. In March, a female suicide bomber, apparently targeting Shiite worshippers just before evening prayer services on a busy street, killed dozens in Karbala.
The latest deaths are part of the monthlong fighting in Sadr City, a slum of approximately 3 million people, that has involved U.S. and Iraqi forces battling fighters loyal to radical Shiite militiamen.
In a development related to the Sadr City violence, an adviser to Iraqi Prime Minister Nuri al-Maliki told CNN on Sunday that military assaults against militias in Baghdad will end if the militias meet certain conditions.
The adviser, Ambassador Sadiq al-Rikabi, said the militias must hand in all heavy and medium weapons; hand over people wanted for arrest; and keep out of the affairs of Iraqi security forces, government institutions and reconstruction projects.
Radical Shiite cleric Muqtada al-Sadr -- whose followers make up one of the most prominent militias -- swiftly rejected the idea.
"Al-Maliki's logic is for the government to do what it wants and the way it wants," said Sheikh Salah al-Obaidi, a top aide to al-Sadr.
Al-Sadr issued a cease-fire order for his supporters across Iraq on March 30. The U.S. military said fighting in the neighborhood decreased, but still remained high.
Recently, al-Sadr's supporters have accused al-Maliki's government of not holding up its end of the cease-fire agreement, which includes freeing non-convicted prisoners from the Sadrist movement and halting what they call illegal raids on the cleric's followers.
On Friday, al-Sadr issued a threat to launch an "open war" against U.S. troops "until liberation" if attacks against his followers do not cease.
In other Baghdad incidents Sunday:
• Mortars slammed into many areas of Baghdad, the Interior Ministry official said. The U.S. Embassy confirmed the mortar attacks but didn't release details on damage or injuries in the International Zone, a heavily fortified district -- also known as the Green Zone -- that houses American and Iraqi governmental offices.
• Six mortars hit a residential area in the Shiite Kadhimiya district in northern Baghdad. There were no reports of casualties.
• Three mortars slammed into an industrial area in western Baghdad's al-Amel neighborhood, killing at least one civilian and wounding seven.
• Three mortars also hit the Baladiyat Shiite district bordering Sadr City, wounding five civilians.
• A parked car bomb detonated in the al-Jamia neighborhood in western Baghdad on Sunday afternoon, killing one Iraqi army soldier and wounding nine other people, the Interior Ministry said. Five of the wounded were civilians, and four were soldiers. The bomb targeted an Iraqi army patrol.
• Another car bomb killed one Iraqi civilian and and wounded seven Iraqi policemen near their checkpoint in western Baghdad's Mansour district Sunday afternoon. These attacks come about a week after the the U.S. military warned soldiers about the potential for a rise in car bomb attacks.
• Also, an Interior Ministry official said police found a grave of 50 people north of Diyala's provincial capital of Baquba. The graves were in an area that officials said used to be an al Qaeda in Iraq stronghold. E-mail to a friend
CNN's Mohammed Tawfeeq and Jomana Karadsheh contributed to this report.