A U.S. Army helicopter made a "hard landing" Thursday in northern Iraq, injuring the two-member crew, but the military said the problem was mechanical and not the result of hostile fire.

A car bomb exploded near a motorcade heading to a police officer's wedding in the Sunni militant stronghold of Fallujah in Anbar province, killing at least five people and wounding 10, said police Lt. Wessam Mohammad. The bride and groom were not harmed.

The attack appeared linked to insurgents, who have targeted police officers, politicians and others seen as symbols of the U.S.-backed government.

Baghdad, meanwhile, had a rare day without a series of bombings. One bomb exploded on a minibus carrying employees of the capital's provincial council, killing one person and injuring four in an eastern neighborhood, police said.

The OH-58 Kiowa helicopter went down in the area of Kirkuk, about 180 miles north of Baghdad. The two injured pilots were evacuated to a U.S. military hospital in Kirkuk, U.S. officials said. There was no word on the extent of their injuries.

The helicopter is mostly used in surveillance and some light combat missions.

"Preliminary reporting shows the cause of the hard landing was mechanical and not hostile fire," the statement said.

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Last week, ground fire forced a Black Hawk helicopter to make an emergency landing north of Baghdad, the military said. At least eight other U.S. helicopters have crashed or been brought down by hostile fire in Iraq this year.

A U.S. Marine was killed Wednesday in Anbar province, the military said.

The lull in Baghdad came a day after a car bomb ripped through a bustling shopping district in western Baghdad, killing at least 10 people and wounding about 20.

Wednesday's blast in Baiyaa, a Sunni-Shiite neighborhood, sent flames and debris shooting two stories high, witnesses said. The force of the explosion peeled back corrugated tin roofs. Charred clothing still clung to the remnants of vendors' stalls hours later.

A U.S. military spokesman condemned the bombing as "ruthless" and "barbaric" but said overall violence was down, three weeks into a joint U.S.-Iraqi security crackdown.

"Although we've seen some initial progress, we know our enemies will continue to attempt to disrupt our efforts, and that improving security in Iraq will take time," Rear Adm. Mark Fox said.

On Thursday, the U.S. military said American and Iraqi troops killed 10 militants and seized six weapons stashes in Diyala province northeast of Baghdad. The raids took place over the past three days, it said.

Diyala is a mixed Sunni-Shiite area that has seen increased violence in recent months, as insurgents stream out of Baghdad during a security crackdown there. Attacks on U.S. troops are up 70 percent since last summer, and the number of arms caches discovered in Diyala has more than doubled in that time, U.S. officials have said.

The 10 were killed Monday in Muqdadiyah, a town in Diyala about 60 miles northeast of Baghdad, the military said. Five others were detained in the operation.

Soldiers also discovered more than 50 rocket-propelled grenades, bomb-making materials and a stolen fire truck that was being loaded with explosives, the statement said.

Another cache was discovered the same day in Baqouba, the provincial capital of Diyala, that included a complete mortar system and 150 rounds of ammunition, the military said.

Complete coverage is available in FOXNews.com's Iraq Center.