Three people were killed and two wounded when a mortar round landed on a Sunni mosque in Baghdad's northern al-Wazeriya district on Friday while two people were killed and two wounded by a car bomb near another Sunni mosque in the western al-Jihad district.
Seven people were wounded when a roadside bomb exploded outside a third Sunni mosque in Baquba, a town 64km (40 miles) north of Baghdad in Diyala province, police said.
Two people were killed and four policemen wounded in clashes between police and fighters when the Salman Pak Shia mosque, southeast of Baghdad, came under attack, the US military said.
It said the National Police Headquarters located near the mosque was also attacked.
The military said five of the alleged attackers were captured and detained for questioning.
The attack on the mosques comes a day after a bomb exploded next to a shrine farther to the south, killing 12 Shias including Iranian visitors.
The Iraqi government has imposed a four-hour ban on movement of vehicles on Fridays in Baghdad and Diyala to stop such attacks.
Sadr City raid
Earlier, nine people were killed and 34 wounded when Iraqi soldiers clashed with fighters in a Shia district of Baghdad.
The Iraqi forces came under fire during a raid aimed at an "insurgent leader" in eastern Baghdad, leading to a gunfight, the US military said in a statement.
The US statement did not mention American involvement or any casualties.
Some residents of the Sadr City neighbourhood speculated that the target was a leader of the Mahdi Army, a Shia militia.
The early morning raid came as security forces were searching for Sunni legislator Taysir al-Mashhadani, who was abducted from a nearby Shia area nearly a week ago.
An Iraqi officer with the army division responsible for the Baghdad area said the Americans had provided them with a list of names of people to be arrested in Sadr City.
Iraqi soldiers led the raid while the Americans played a supportive role, but nobody was arrested because of the clashes, the officer said.
Local officials gave conflicting accounts.
Lieutenant Qadhim Abbas Hamza of the Sadr City police said fighter planes also fired from the air at about 3.15am and nine people, including a woman, were killed and 14 wounded. He said eight people were arrested.
A hospital official said seven people were killed and 34 wounded.
Witnesses of Friday's attack also said warplanes fired on the area, wounding some people who were sleeping on the roof, a common practice amid searing temperatures and electricity shortages in Iraq.
In another statement, the US military said it killed two fighters and detained five others during a raid on Friday near the city of Baquba, north of Baghdad.