PUL-E-ALAM, Afghanistan — Militants brandishing assault rifles ambushed a New York-based relief organization’s vehicle south of Kabul today, killing three Western aid workers and their Afghan driver and leaving their white SUV riddled with hundreds of bullets, officials said.

The three women killed in Logar province worked for the International Rescue Committee, a spokeswoman for the group, Melissa Winkler, said. One was a dual American-Trinidadian citizen, one was Canadian, and the third was a dual British-Canadian citizen, the IRC said.

Five gunmen armed with assault rifles stepped out of a small village area and fired at the IRC vehicles, the deputy counterterrorism director in Logar, Abdullah Khan, said, citing an Afghan IRC employee injured in the attack who was traveling in a second vehicle. Mr. Khan said the women’s vehicle, a white SUV, was hit by hundreds of bullets. It had stickers on the side of the vehicle saying IRC.

An IRC driver, Abdurrahman Khan, was sobbing as he loaded two of the bodies onto the back of a truck at Logar province’s Pul-e-Alam hospital.

“They were here helping Afghan people,” the driver said. “They were not carrying weapons.”

At the hospital, Dr. Mir Mabub Shah said all four bodies had multiple bullet wounds. Three female Afghan nurses were covering the three victims in a white cloth shroud as they placed them in wooden coffins.

The women were traveling to Kabul from the eastern city of Gardez when they were attacked.

The top U.N. official in Kabul, Kai Eide, called it a “cowardly attack.”

“The IRC provides life-saving humanitarian assistance to those most affected by the conflict, and it is reprehensible that such selfless individuals working for the most vulnerable communities should be deliberately targeted,” Mr. Eide said.

“We face a growing humanitarian challenge in Afghanistan, and all parties to this conflict must recognize and respect the inherent neutrality and independence of the humanitarian assistance being provided to those Afghans who need our help the most,” he added.

The International Rescue Committee provides emergency relief, rehabilitation, protection of human rights, and post-conflict development in countries around the world, according to its Web site.

Two Afghan IRC staff members were shot and killed in Logar in July 2007 while driving to work on the National Solidarity Program, a government-led program that carries out development projects.

Despite the deteriorating security situation in Afghanistan, the IRC said in July it was carrying on with its projects but has had to reduce the levels of its work.

Attacks against aid workers in Afghanistan have spiked this year. Today’s attack brings to at least 23 the number of aid workers killed in militant attacks in 2008, compared with 15 killed in all of 2007, according to a recent report from ANSO, a security group that works for aid organizations in the country.

ANSO said 2008 was on track to be the deadliest year for aid workers in Afghanistan since the 2001 American-led invasion that ousted the Taliban. ANSO reported a 50% increase in insurgent attacks around the country in 2008 over 2007.

More than 3,200 people have died in insurgency related violence this year, according to an Associated Press count based on Western and Afghan officials.