A U.S. helicopter crashed north of the Iraqi capital on Monday, killing two American soldiers on board, and two Marines and a soldier were killed in fighting in the country's restive Anbar province.

The military said no gunfire was reported in the area at the time of the helicopter crash. The incident occurred in Salahuddin province, which includes Saddam Hussein's hometown of Tikrit and was under curfew because of Sunday's verdict and sentencing of the former Iraqi leader.

With the helicopter crash and the Anbar deaths, the number of U.S. troops killed this month in Iraq rose to 18 and follow a particularly violent month for the American military in Iraq, which saw 105 deaths in October.

Still missing was a U.S. soldier kidnapped last month in Baghdad, and the man's Iraqi uncle said Monday he believed his nephew's abductors belong to a "well organized" rogue cell from the Shiite Mahdi Army militia of the anti-U.S. cleric Muqtada al-Sadr.

Entifadh Qanbar, the uncle, said he had received a $250,000-ransom demand from the kidnappers, through an intermediary. He had in turn demanded proof that his nephew was alive and well before entering negotiations.

The U.S. military said last week that that there was "an ongoing dialogue" to win the release of Ahmed Qusai al-Taayie, a 41-year-old reserve soldier from Ann Arbor, Mich. Al-Taayie was visiting his Iraqi wife when he was handcuffed and taken away by gunmen during a visit to the woman's family.

U.S. officials, like Qanbar, said there had been no news of the missing soldier.

"We continue to conduct operations based on actionable intelligence to find our soldier," Lt. Col. Christopher Garver said Monday. "His safe return is obviously a top priority."

Qanbar, a former spokesman for the National Congress Party of senior Iraqi politician Ahmad Chalabi, said he had contact with the kidnappers through an intermediary in Baghdad, but had not heard from them since Saturday when he demanded that he be shown proof that al-Taayie was alive.

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"I want to see him next to the same day newspaper or in a video. I want him to answer certain questions. Any proof that he is still alive," Qanbar told The Associated Press by telephone from Amman, in neighboring Jordan.

Qanbar said he believed a man he identified as Majid al-Qais Omran, also known by his nickname Abu Rami, is responsible for the kidnapping and said he believed he was the leader of an experienced gang.

"It is a very capable gang with a great deal of resources," said Qanbar, "They identified themselves as Mahdi Army members, but I believe they belong to a breakaway cell of the Mahdi Army. Their conduct suggest they have experience in this line of work."

The soldier's wife and two of her siblings have been taken by American troops to the Green Zone, where they were being kept for their safety.

The military was withholding the names of the latest fatalities pending notification of their families, but it identified both Marines as having been assigned to Regimental Combat Team 5. A brief statement from the military said one Marine died on Saturday from wounds received in combat, while the other was wounded in fighting on Saturday and died Monday.

The statement said the soldier had been assigned to 1st Brigade, 1st Armored Division, and died on Monday from wounds received in combat. The statement didn't say when he was wounded.

Despite the curfew imposed for the Saddam verdict, the relentless death toll continued among Iraqis as well: The bodies of 50 murder victims were discovered Sunday, the bulk of them in Baghdad, police 1st. Lt. Thaer Mahmoud said.

Mortars slammed into a Sunni neighborhood in northern Baghdad, although no damage or casualties were immediately reported. Other parts of Baghdad were quiet, with offices and the international airport closed and few cars or pedestrians on the streets.

Among U.S. forces, October was the fourth deadliest month for American troops since the war began in March 2003. The U.S. lost 107 troops in Iraq in January 2005; at least 135 in April 2004, and 137 in November 2004.