At least 28 Iraqis and five U.S. service members were killed in attacks on Thursday as a U.S. helicopter hit by ground fire was forced to make an emergency landing and four kidnapped Americans and an Austrian were believed to be alive after a video surfaced following their abduction six weeks ago.

The U.S. Army OH-58 Kiowa helicopter landed safely at 1:35 p.m. local time at a U.S. base, Camp Brassfield-Mora, said U.S. Air Force Capt. Matt Hasson at U.S. Central Command forward headquarters in Doha, Qatar.

No one was injured, Hasson said. The Kiowa is a scout helicopter that normally carries a two-person crew.

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In Baghdad, a homicide bomber carrying two empty plastic containers joined a crowd of people lining up to buy kerosene near a stadium, said Brig. Abdul-Karim Khalaf, a spokesman for the Iraqi Interior Ministry. The attacker then detonated his explosive-laden belt, killing at least 10 people and injuring 20 others.

Two bombs also exploded opposite a park in the South Gate area of Baghdad, killing nine people and wounding 43, a police officer said on condition of anonymity because of security concerns.

Another blast targeted a police patrol in western Baghdad but missed, killing two civilians instead, police said. Four people were wounded.

Gunmen wearing police uniforms attacked an army checkpoint in the city of Balad north of Baghdad, killing three Iraqi troops and wounding eight people, authorities said. A bomb also killed an Iraqi soldier in a military vehicle near Qazaniya, close to the Iranian border, police said.

Regarding the American and Austrian men who disappeared Nov. 16 when a convoy of trucks being escorted by their Crescent Security Group was hijacked on a highway near Safwan, a city on the border with Kuwait, "At this time, U.S. officials believe the American citizens are still being held by their captors," said Lou Fintor, a spokesman for the U.S. Embassy in Baghdad.

Suspected militiamen dressed in Iraqi police uniforms ambushed the convoy, taking 14 hostages, including the five security guards, and nine truck drivers who were later released.

"The State Department continues to be in touch with the families of the U.S. citizens. We strongly condemn the kidnapping and call on the hostage-takers to release these people immediately," Fintor said.

A video of the kidnapped Americans reportedly surfaced this week, showing them alive and in good condition. The footage, reported by McClatchy Newspapers, was believed to have been made about a month ago. If authentic, it would be the first proof that all five men survived the ambush.

U.S., British and Iraqi forces have all conducted raids in the search for the five men. Raids were carried out in several areas north of Basra, the southern city where most of the 7,200 British soldiers in Iraq are based.

Meanwhile, the U.S. military on Thursday announced the deaths of four American soldiers and a Marine in Iraq.

A roadside bomb killed a soldier and wounded another on Thursday while they were on a foot patrol north of Baghdad, the military said in a statement.

On Wednesday, two soldiers were killed when a bomb exploded southwest of Baghdad, according to the military. Another soldier was wounded in the explosion.

Another soldier was killed in an eastern section of the Iraqi capital on Wednesday, the military said. The unit was on a route-clearing mission when a roadside bomb exploded. Two soldiers were wounded.

A Marine assigned to Regimental Combat Team 5 was killed during combat in Iraq's western Anbar province Wednesday, the military said.

With 100 American troops dead so far this month, December is the second-deadliest month of 2006 for U.S. military personnel. Some 105 troops died in October.

"This has been a difficult month for coalition forces," Maj. Gen. William Caldwell, a spokesman for U.S. forces in Iraq, told reporters Wednesday.

"And the month is not over yet," Caldwell said. "Our deepest condolences to those families and friends who've lost someone near and dear to them."

At least 2,988 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.