BAGHDAD (AFP) - A series of tit-for-tat attacks on Shiite and Sunni mosques killed at least 17 people in Iraq on the Muslim day of prayer Friday, triggering fears of a new upsurge in sectarian violence.

At least 30 people were also killed or wounded in deadly clashes in Baghdad's Shiite slum district of Sadr City between Shiite militiamen and U.S.-Iraqi forces who claimed to have captured a leading insurgent there.

Fears of sectarian bloodshed rose again as at least five mosques were attacked across the country -- three of them Sunni -- the day after a car bomb exploded next to a Shiite shrine in Kufa, south of Baghdad, that killed 12 Shiites, most of them Iranian pilgrims.

Friday's attacks served as a reminder of the bombing of a revered Shiite shrine in Samarra in February that set off a wave of Shiite-Sunni communal bloodshed that continues to this day.

Sunni religious leaders were also attacked.

Sunni MP Adnan al-Dulaimi's party claimed that a police commando force and sectarian militias had kidnapped and killed Sheikh Said Mohammed Taha al-Samarrai, imam of a mosque in the town of Mahmudiyah, south of Baghdad.

Sheikh Abdel Ghafur al-Sammarai, the head of the Sunni religious endowment authority, also said in his Friday sermon that another imam of a Baghdad mosque, Sheikh Alaa Mohammed Abbas al-Rikabi, had been kidnapped.

The kidnapping of Shiekh Alaa, 65, could not be confirmed, but family and friends contacted by AFP said they had not seen him for two days.

"Militias must be dismantled and the police force must be reconstructed otherwise they will burn down Baghdad and the fire will destroy everyone," warned Samarrai, who claimed 181 Sunni clerics have been killed since February.

In the deadliest attack Friday at least nine people were killed and 59 wounded, 20 of them seriously, when a car bomb went off against worshippers coming out of a Shiite mosque in the village of Tal al-Banat near the town of Sinjar, west of the main northern city of Mosul.

Local police said the bombers parked the car close to the mosque and fled the area. Some of the wounded were admitted to a nearby U.S. military base hospital, while a few were transferred to Sinjar and Tall Afar.

Two civilians were killed and three wounded when a car bomb exploded near the Fakhri Shanshal Sunni mosque in Baghdad's western Jihad neighborhood.

Another three people were killed and seven wounded when a mortar round exploded in front of the Sunni Al-Nidaa mosque in the capital's northern Al-Qahira neighborhood as the faithful assembled for weekly prayers.

In Baquba, northeast of Baghdad, a roadside bomb exploded as worshippers emerged from the Sunni Ahmed bin Hanbal mosque, killing one person and wounding four.

Another two Iraqis were killed and four policemen wounded in clashes between police and rebels when the Shiite mosque in Salman Pak southeast of Baghdad was attacked.

The U.S. military said the main police station was also hit.

Meanwhile, at least 30 people were killed or wounded in gunbattles between Shiite militiamen and U.S.-Iraqi forces in Sadr City, the U.S. military and security sources said.

The military said a "high-level insurgent leader" behind attacks on Iraqi and U.S.-led forces was captured, but did not name him.

"An estimated 30-40 enemy fighters were killed or wounded in the 43-minute firefight," it said.

Sources in the defense and interior ministries said the clashes between U.S.-led forces and firebrand Shiite cleric Moqtada al-Sadr's Mehdi army lasted for four hours and left at least nine people dead and 30 wounded.

Sahib al-Amiri, an official in Sadr's movement, said the U.S. forces had detained a Shiite imam from the district, Adnan al-Oneibi.

Four bodies showing signs of torture were also recovered in the village of Suwera, 50 kilometers south of Baghdad, while three people were killed and 35 wounded when several mortars were fired at a market in Baghdad's Shuala neighborhood.

Major General Ahmed al-Awad of Iraqi army said that his forces had arrested 56 suspects while pursuing Rasheed Taan, who ranks number six on Iraq's 41 most wanted list.

The list released last week says Taan provides command, control and finance to the anti-coalition effort in Diyala province and carries a bounty of one million dollars.

In other developments, Japan started withdrawing its troops from Iraq with the first batch of 38 soldiers of some 600 troops being flown to Kuwait from the southern province of Muthanna.

Japan ordered its troops to leave Iraq on June 20, ending its first military mission since World War II to a country where fighting is under way.