A militant group beheaded three Iraqi Kurdish hostages, showing the killings in a videotape posted on a Web site on Sunday, while another group announced that it had kidnapped at least 15 Iraqi National Guardsmen.

A statement accompanying the video of the beheadings was signed by the Army of Ansar al-Sunna, a group that said it had killed 12 Nepalese hostages in August. The statement said the Kurdish hostages were beheaded as "an example to others, and for us to revenge our women, children and elderly who die daily from American raids."

Sarkawt Hassan, a security official in the predominantly Kurdish city of Sulaymaniyah, told the Associated Press that the three men were pesh merga, militia fighters for the regional Kurdish government. Their bodies were found near a road outside the northern city of Mosul, Hassan said.

The al-Jazeera satellite television network aired a brief videotape showing gunmen surrounding what it said was a group of Iraqi National Guardsmen. A previously unknown organization calling itself the Brigades of Mohammed bin Abdullah threatened to kill the men within 48 hours unless Iraqi authorities released an aide to the rebellious Shiite cleric Moqtada Sadr.

U.S. and Iraqi security forces arrested the aide, Hazim Araji, during a raid Sunday morning, according to local television reports. Araji is Sadr's spokesman in the Kadhimiya district of Baghdad.

In a third incident, three Lebanese men and their Iraqi driver were also reported kidnapped on Sunday, according to the AP, which quoted an unidentified official at the Lebanese Embassy as saying that the men were taken hostage Friday night while driving on a road between Baghdad and Fallujah.

The kidnappings have added another macabre dimension to the escalating violence across Iraq. Among the hostages still being held are two American contractors, Jack Hensley and Eugene "Jack" Armstrong, and a British engineer, Kenneth Bigley, who were kidnapped on Thursday in Baghdad; two French journalists, Georges Malbrunot and Christian Chesnot, who were kidnapped Aug. 19 en route to Najaf; and two Italian aid workers, Simona Pari and Simona Torretta, kidnapped Sept. 7 in the capital.

After meetings in London with British Prime Minister Tony Blair, Iraq's interim prime minister, Ayad Allawi, said Iraqi officials were "trying our best working on the issue of hostages and hopefully we will achieve some good results."

On Saturday, an organization linked to a Jordanian militant, Abu Musab Zarqawi, threatened to kill the American and British hostages within 48 hours unless all Muslim women held at the Abu Ghraib prison near Baghdad and at another prison in the southern city of Umm Qasr were released.

The Iraqi minister of foreign affairs, Hoshyar Zebari, also in London, told BBC television, "Really, our policy is not to negotiate with the terrorists."

Allawi, who is scheduled to make his first visit to the United States this week, said the escalating violence would not prevent Iraq from conducting nationwide elections in January. He said the elections were crucial to stopping the insurgency, which has left at least 250 people dead and hundreds injured in the past week alone.

"January next I think is going to be a major blow to terrorists and insurgents," said Allawi, according to the Reuters news agency. "Once we go through the democratic process, once we achieve and progress toward democracy, the terrorists will be defeated."

Meanwhile, a car bomb exploded in an apparent suicide attack Sunday near a joint patrol of U.S. and Iraqi forces close to the city of Samarra, about 65 miles north of Baghdad, according to Lt. Wayne Adkins, a spokesman for the 1st Infantry Division. The blast killed an Iraqi soldier and an Iraqi civilian and wounded seven people, including four U.S. soldiers.

The attack was the first of any significance in the city since U.S. forces moved in on Sept. 9 to reinstate the local government, which had been driven out by insurgents. Adkins said the driver of a sedan detonated a bomb as the U.S.-Iraqi patrol approached the vehicle.

Adkins said the attack would not prevent U.S. troops from continuing to patrol the area. He said the only other incident in Samarra since U.S. forces entered the city occurred on Sept. 15, when insurgents fired an errant rocket-propelled grenade at U.S.-led forces during a city council meeting.

"We've been very happy with the progress in Samarra," Adkins said.

An Iraqi policeman takes protective aim during the investigation of a shooting incident in Baghdad in which three of his colleagues were injured.