A militant group posted a video on the Internet purporting to show militants sawing off the heads of three Iraqi members of a Kurdish party for cooperating with U.S. forces. Another group claimed to have kidnapped 15 members of the Iraqi National Guard.

Despite the unrelenting violence, Iraqi Prime Minister Ayad Allawi (search) said that his interim government was determined "to stick to the timetable of the elections," which are due by Jan. 31.

"January next, I think, is going to be a major blow to terrorists and insurgents," said Allawi, who spoke with reporters Sunday after a meeting with British leader Tony Blair in London. "We are adamant that democracy is going to prevail, is going to win in Iraq."

Allawi, a secular Shiite Muslim, has been insistent about holding elections on time because of pressure from Iraq's majority Shiite community and its most powerful cleric, Grand Ayatollah Ali al-Sistani, who fears the interim arrangement will be prolonged.

Allawi now heads to the United Nations for this week's General Assembly session.

Last week, U.N. Secretary-General Kofi Annan (search) warned there could not be "credible elections if the security conditions continue as they are now." Some 300 people have been killed in escalating violence over the past week, including bombings, street fighting and U.S. airstrikes.

Several cities in the Sunni Muslim heartland north and west of Baghdad are out of U.S. and Iraqi government control, with insurgents holding sway, particularly in the city of Fallujah. That raises questions on whether balloting can be held there — and the legitimacy of elections held without adequate Sunni participation.

In another sign of continuing instability 17 months into the U.S.-led occupation of Iraq, a suicide car bomb killed three people in Samarra — a northern city that U.S. and Iraqi commanders have portrayed as a success story in their attempts to put down the insurgency.

In the United States, Republican and Democratic senators urged President Bush on Sunday to face the reality of the situation in Iraq and change its policies. A major problem, said leaders of the Senate Foreign Relations Committee on CBS' "Face the Nation," was incompetence by the administration in reconstructing the country's shattered infrastructure.

"The fact is a crisp, sharp analysis of our policies is required. We didn't do that in Vietnam, and we saw 11 years of casualties mount to the point where we finally lost," said Sen. Chuck Hagel, a Vietnam War veteran who is co-chairman of Bush's re-election committee in Nebraska.

Near the northern Iraqi city of Mosul, the decapitated bodies of the three slain Kurdish hostages were found on a road, said Sarkawt Hassan, security chief in the Kurdish town of Sulaimaniyah. He said the three were members of the peshmerga militia of the Kurdistan Democratic Party.

The videotape, posted Sunday on a site known for its Islamic militant content, shows three young men, two of whom hold up identity cards. Seconds later, each has his throat slit and his head placed on the back of his body.

The Ansar al-Sunna Army — a Sunni militant group that said it killed 12 Nepalese hostages in August and carried out Feb. 1 suicide attacks against Kurdish political parties that killed 109 people — claimed responsibility for the beheadings in a statement with the video.

It said the three were KDP members snatched as they were transporting military vehicles to a base in Taji, 15 miles north of Baghdad.

The group said it was targeting Iraqi Kurdish parties because they have "sworn allegiance to the crusaders and fought and are still fighting Islam and its people."

The tape and the statement could not be independently verified.

Later, the Arab news station Al-Jazeera aired a separate video claiming 18 captured Iraqi soldiers would be killed unless a detained aide of rebel Shiite cleric Muqtada al-Sadr was freed in 48 hours. The men in military dress were shown seated at gunpoint in the video from a group calling itself the Brigades of Mohammed bin Abdullah.

No audio was aired, but Al-Jazeera's announcer said the militants threatened to kill the 18 unless Hazem al-A'araji, who was detained in a raid by U.S. and Iraqi forces on al-Sadr's Baghdad offices on Saturday, is freed.

The videos surfaced the day before the Tawhid and Jihad group, led by Jordanian terror mastermind Abu Musab al-Zarqawi, has threatened to behead Americans Jack Hensley and Eugene Armstrong and Briton Kenneth Bigley, who were seized from their Baghdad house last week.

The group, which has claimed responsibility for a series of bombings and hostage takings, demands the release of Iraqi women from the American controlled Abu Ghraib and Umm Qasr prisons.

Abu Ghraib is the prison where U.S. soldiers were photographed sexually humiliating male prisoners, but the U.S. military says no women are held at either facility, though it says it is holding two female "security prisoners" elsewhere.

More than 100 foreigners have been kidnapped in Iraq, some for lucrative ransoms, and many have been executed. At least five other Westerners are currently being held hostage here, including an Iraqi-American man, two female Italian aid workers and two French reporters.

Lebanon's Foreign Ministry said Sunday that three Lebanese men and their Iraqi driver were abducted by gunmen on the Baghdad-Fallujah highway Friday night. The four worked for a travel agency that has a branch in Baghdad, a Foreign Ministry official said.