A series of mortar barrages killed eight civilians and wounded 25 others early Saturday in a Sunni enclave surrounded by Shiite areas in central Baghdad, police said, while a key bridge was damaged by a bomb in northern Iraq.

The mortars began slamming into the Fadhil area in Baghdad at 1:30 a.m. and continued sporadically until 7 a.m., damaging five houses, a policeman said, speaking on condition of anonymity as he was not authorized to deal with the media. A woman and a child were among the eight dead, he said.

Baghdad's Sunni and Shiite neighborhoods frequently exchange mortar and other fire in Iraq's continuing sectarian conflict.

Elsewhere in the capital, residents in the Sunni neighborhood of Amariyah remained under curfew as U.S. and Iraqi troops sought to maintain calm in the area after fierce clashes between rival insurgent groups and Al Qaeda in Iraq.

Firas al-Azzawi, a 32-year-old father of two, said he closed his electronics shop when the clashes began earlier this week. He said people were converging on the few stores that were open to buy food, including one grocer who brought in fresh vegetables by loading them in handcarts.

He said the grocer was rationing how much he sold "because there was not enough for everyone who were waiting in a line to buy."

"There is no electricity, no water and no fuel. Street generators stopped feeding the area with power during daytime because of fuel shortage. They only provide power for few hours during the night," he said.

Despite the discomfort, he welcomed the presence of the U.S. and Iraqi troops patrolling the streets.

"I feel very comfortable when I see the American and the Iraqi troops because we are fed up with Al Qaeda, which kept on threatening us and our businesses everyday," he said. "They were ordering us to close our shops because they were carrying out operations. They also have started killing Sunnis as well."

In northern Iraq, a bomb heavily damaged the Sarhat Bridge, a vital link on a major road connecting Baghdad with northern Iraq, including the Kurdish cities of Irbil and Sulaimaniya, as well as Tikrit and Kirkuk, police said.

Small cars were still able to cross the bridge but the damage caused by the explosion was forcing trucks to take a more dangerous route through Sunni cities and the volatile Diyala province, police Brig. Gen. Sarhat Qadir said.

A U.S. helicopter also was forced to make a precautionary landing north of Baghdad on Saturday, but nobody was injured, military spokeswoman Lt. Col. Josslyn Aberle said.

The aircraft, which went down in the volatile Diyala province, was being recovered, and the reason for the precautionary landing was under investigation, she added, declining to give more specifics due to security concerns.

The incident came five days after two U.S. soldiers were killed when their OH-58 scout helicopter was shot down in Diyala, which has been the scene of fierce fighting between militants and U.S. forces in recent months. Six other U.S. troops were killed in an insurgent roadside bomb ambush as they raced to the site of the crash on Monday.

The U.S. military, meanwhile, reported another soldier was killed in a roadside bombing Wednesday in Baghdad, raising to at least 127 the number U.S. troop deaths in May, the third-deadliest month for American forces since the war started in March 2003. It followed April 2004, when 135 Americans died and November 2004 with 137.

May also was the third-deadliest for Iraqis since The Associated Press began tracking civilian casualties in April 2005. At least 2,155 Iraqis were killed last month, according to the AP count. Interior Ministry officials said the Iraqi government put the number at 2,123.

The deadliest months in the past two years were December 2006, when at least 2,309 were killed, and November 2006, when at least 2,250 were killed.

In other developments:

— A prominent Sunni sheik, Ali Khudir al-Zind, was killed in a drive-by shooting as he walked near his home in western Baghdad, police said. Elsewhere in western Baghdad, gunmen opened fire in two separate locations in western Baghdad, killing three people, and police found two bullet-riddled bodies of people who had been bound and blindfolded and showed signs of torture.

— U.S.-led forces killed one suspected insurgent and detained eight in a series of raids outside the capital.