BAGHDAD, Iraq (CNN) -- Three suicide bombers and a car bomb in the northern Iraqi city of Mosul on Saturday capped off a day of nationwide violence that left at least 15 people dead and 94 wounded, police and Iraqi officials said.
Six people were killed and five were hurt when a suicide bomber wearing an explosive vest walked up to an Iraqi police checkpoint in Mosul, according to an Interior Ministry official.
Two of the dead were police officers.
Earlier, a suicide bomber slammed his car into an Iraqi army checkpoint in Mosul's Al-Tahreer neighborhood, a police official said.
Six people were wounded, Iraqi officials said. The U.S. military said two Iraqi citizens were killed.
A third suicide bomber detonated an explosives-packed fuel tanker in the city's western al-Ruman area, wounding 15 civilians, the official said. The U.S. military said 40 people were wounded, 30 of them Iraqi soldiers.
The fourth attack was a parked car bomb, which exploded in the southern Al-Tayran area and wounded five people, the official said.
In other fatal incidents, three Iraqi soldiers died when a roadside bomb struck their patrol in Diyala province north of Baghdad, about 3 miles east of Baquba, on Saturday morning, the Interior Ministry official said.
In the western Baghdad neighborhood of Amriya, a suicide car bomb exploded outside the office of the local awakening council, killing two members and wounding eight, an Interior Ministry official said. The attack happened about 1:30 p.m. local time, as the members were leaving their meeting.
Among the wounded was Abu al-Abed, the leader of the Amriya awakening council, the officials said. Al-Abed has been credited with stabilizing the Amriya neighborhood.
In the western Baghdad neighborhood of Maamoun on Saturday, three gunmen stormed a store and killed the owner, an Interior Ministry official said.
When Iraqi security forces arrived minutes later, a bomb inside the store exploded, wounding 10 people, including two Iraqi soldiers.
A police officer was killed when gunmen attacked a patrol in the town of Sheikh-Saad, about 18 miles north of Baquba, on Saturday morning, the official said.
In other incidents:
• Three Iraqi soldiers were wounded when a roadside bomb exploded near their patrol in northeastern Baghdad's Sleikh neighborhood at 10 a.m. Saturday, an Interior Ministry official said
• Gunmen in a car opened fire on traffic police in central Baghdad's al-Wathiq square, wounding five people, about 10:30 a.m., the official said. Those hurt included three police officers and two pedestrians, the official said.
• In central Tikrit, a roadside bomb wounded eight people, including four Iraqi police officers, Saturday morning, a Tikrit police official said. Police said the bomb targeted a police patrol on al-Arbaeen Street in Tikrit, a major Sunni city in Salaheddin province, about 100 miles north of Baghdad.
• In the northern city of Kirkuk, a roadside bomb wounded two Iraqi police officers on Saturday afternoon, police said.
• A roadside bomb near a house in central Baquba's al-Hay neighborhood wounded two Iraqi civilians Saturday morning, the official said.
Overnight violence in Baghdad's Sadr City killed eight people and wounded 28 others, an Interior Ministry official said. The official said U.S. airstrikes and clashes caused the casualties in Sadr City. Two of the dead were children, the official said.
The U.S. military said an unmanned aerial vehicle killed two "special groups criminals" in Sadr City about 3:20 p.m. Saturday. The vehicle's operators saw the people putting weapons into a vehicle and attacked that vehicle with a Hellfire missile, the military said in a statement.
A munitions cache and a weapons cache were seized Saturday by U.S. troops and Iraqi police, the military said.
"We continue to conduct precision targeting against special group criminals in order to provide security and stability for the people of Baghdad," said Lt. Col. Steven Stover, a U.S. military spokesman in Baghdad.
Fighting in Sadr City, which has been going on for a month, has involved U.S. and Iraqi forces battling Shiite militia members.
South of Baghdad, Iraqi firefighters brought a pipeline blaze, ignited by an accidental explosion Friday evening, under control early Saturday, Iraqi officials said.
The oil fire happened at 7:39 p.m. on a pipeline southwest of Iskandariya in Babil province, a U.S. military statement said.
The blast was "was caused accidentally by maintenance personnel," the commander of the Karbala Operations Center said.
He said the fire was contained by 1:30 a.m. and was extinguished a short time later. E-mail to a friend
CNN's Mohammed Tawfeeq and Jomana Karadsheh contributed to this report.