A U.S. helicopter carrying 16 Marines made an emergency landing in a lake in a volatile province west of Baghdad, killing four of them, the military said Monday.

The military said the CH-46 helicopter from 3rd Marine Aircraft Wing made the emergency landing Sunday near the shore of Lake Qadisiyah "in which the pilots maintained control of the aircraft the entire time."

It said the helicopter had experienced mechanical problems and was not hit by enemy fire.

Twelve passengers survived the crash; a Marine was pulled from the water but attempts to resuscitate him were unsuccessful. A search was then conducted for three missing Marines whose bodies were found, the military said.

The crash occurred in Anbar province, where many of Iraq's Sunni Arab insurgent groups are based and where many U.S. Marines die in battles with the militants.

A U.S. fighter jet crashed last week in a field in Anbar, killing the Air Force pilot on board. And over the weekend, at least 10 American service members died, including five in Anbar.

U.S. forces recently acknowledged that their stepped-up effort to stop a wave of Sunni-Shiite violence in Baghdad had failed. That was clear on Nov. 23, when a bombing and mortar attack killed 215 people in Baghdad's Shiite district of Sadr City, the deadliest single attack during the Iraq war.

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On Saturday, a triple car bombing struck a food market in a predominantly Shiite district of Baghdad, killing 68 people, police said.

Drive-by shootings and a suicide car bomber killed at least seven Iraqis and wounded five on Monday. American forces also said they killed two militants and destroyed a vehicle packed with explosives.

"We condemn in the strongest language the recent car bombings, attacks and retribution killings by extremists against peaceful Iraqis in Baghdad," U.S. Ambassador Zalmay Khalilzad and U.S. Gen. George W. Casey, Jr., the top American military commander in Iraq, said Monday in a joint statement.

"The true enemies of all Iraqis are the murderers who carry out these senseless and cowardly attacks, regardless of sect, tribe or ethnicity. They are terrified of progress in this country and are determined to sow sectarian discord for their own selfish agenda," they added.

"We implore all Iraqis not to become pawns of those who seek to destroy you and your country. Do not allow yourself to be drawn down the road of senseless brutality by striking back."

Abdul-Aziz al-Hakim, one of Iraq's top Shiite politicians, was scheduled to meet with Bush on Monday in Washington to discuss issues expected to include the failure of Iraq's Shiite-dominated government to reduce sectarian violence in cities such as Baghdad.

Over the weekend, al-Hakim and other Iraqi politicians rejected Annan's proposal for an international conference on Iraq, saying it would be unrealistic to debate the country's future outside the country.

In Monday's worst attack, suspected militants killed three government agricultural engineers and their driver in a drive-by shooting as they headed to work Monday morning in Baqouba, northeast of Baghdad. A similar attack killed a man and woman driving in a town in the same area. The deaths were reported by police who spoke on condition of anonymity to protect their safety.

In Baghdad, a news editor at an Iraqi radio station that provides news and educational programming was shot and killed as he traveled to work, said Karim al-Youssif, an assistant manager at the private, independent station that was founded in 2004.

Nabil Ibrahim al-Dulaim, a member of Iraq's Sunni Arab minority, was married with two young daughters, al-Youssif said, calling his colleague "another victim of the campaign against journalists in this country."

Al-Dulaim's slaying raised to at least 93 the number of journalists who have been killed in Iraq since the Iraq war began, according the Paris-based Reporters Without Borders. Forty-five other media employees -- including drivers, interpreters and guards -- also have been killed, all of them Iraqi except for one Lebanese.

In the northwestern city of Mosul, a suicide car bomber attacked a U.S. military convoy and wounded five nearby Iraqi civilians, said Dr. Bahaldin al-Barki, who works at the hospital where they were taken. No U.S. casualties were reported.

In northern Baghdad, American forces killed two insurgents and detained six during a raid on buildings where insurgents with ties to Al Qaeda in Iraq were making car bombs, the U.S. command said. A weapons cache including artillery rounds and AK-47s also was found.

On Saturday and Sunday, eight U.S. soldiers and a Marine died, and two soldiers were wounded, in Baghdad or north of the capital. The deaths raised to at least 2,898 the number of U.S. military personnel killed in the war that started in March 2003, according to an Associated Press count.

On Sunday, two Iraqi boys, ages 10 and 15, were wounded in an attack on coalition forces during which insurgents fired a rifle grenade in Haditha, 140 miles northwest of Baghdad, the U.S. command said. The coalition forces, who suffered no casualties, detained two Iraqis believed to have been involved in the attack.

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