The ambush of two clearly marked aid vehicles on the main road south of Kabul was the latest in a record number of attacks on aid groups this year a surge that has workers questioning if they can safely provide services in remote and dangerous areas where help is most needed.
The group whose workers were slain, the New York-based International Rescue Committee, announced it was suspending its Afghan humanitarian programs indefinitely.
The Taliban claimed responsibility for the killings, saying its fighters attacked two vehicles of "the foreign invader forces."
"They were not working for the interests of Afghanistan and they belonged to those countries whose forces ... took Afghanistan's freedom," Taliban spokesman Zabiullah Mujahid told The Associated Press in a phone call from an undisclosed location.
Mujahid called the women spies, a frequent Taliban accusation against its targets.
The aid group said the three women killed in Logar province were a dual Trinidadian-American citizen, a Canadian and a dual national British-Canadian.
"These extraordinary individuals were deeply committed to aiding the people of Afghanistan, especially the children who have seen so much strife," said George Rupp, president of the International Rescue Committee.
The women were driving from the eastern province of Paktia to Kabul in a white SUV marked with IRC stickers, said Abdullah Khan, deputy counterterrorism director in Logar.
Five men armed with Kalashnikov assault rifles stepped out of a village area and fired at the two aid vehicles, Khan said, citing a report from an Afghan IRC employee wounded in the second vehicle. The women's white SUV was hit by dozens of bullets, Khan said.
At the Pul-e-Alam hospital, IRC driver Abdurrahman Khan wept while helping load two of the victims' bodies onto the back of a truck.
"They were here helping Afghan people," he said. "They were not carrying weapons."
All four victims suffered multiple bullet wounds, Dr. Mir Mabub Shah said as three female Afghan nurses shrouded the three dead women in white cloth before putting them in wooden coffins.
With Wednesday's attack, at least 23 workers have been slain by militants in 2008, compared with 15 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 is on track to be the deadliest year for aid workers in Afghanistan since the U.S.-led invasion ended Taliban rule in late 2001.
"The car was clearly marked. They were clearly not military personnel and this is a major concern not only to us but to all those who are in humanitarian community in Afghanistan," said Aleem Siddique, a spokesman for the United Nations mission in Afghanistan.
The International Rescue Committee has been working in Afghanistan for 20 years. In the 1980s, the group provided medical aid to Afghan refugees fleeing into Pakistan during the Soviet occupation.
Since the ouster of the Taliban's hard-line Islamic regime, the group has also been involved with the National Solidarity Program, a community-based development program funded by the World Bank through the Afghan government and implemented by international aid groups.
Anna Husarska, a senior policy adviser for IRC, wrote in an opinion piece for Los Angeles Times in May that insurgents are attacking all those seen as helping the government of Afghan President Hamid Karzai.
"Since they oppose the current government, they also oppose those who work with it," she wrote. "And unfortunately, they don't differentiate among armed multinational forces, security contractors and humanitarian groups."
Kai Eide, the top U.N. official in Kabul, called the assault a "cowardly attack."
"The IRC provides lifesaving 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," Eide said.
The International Rescue Committee provides emergency relief and rehabilitation and works for 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 to death in Logar in July 2007 while working on the National Solidarity Program. Despite rising violence in Afghanistan, the group said in July that it was carrying on with its projects but had to reduce the levels of its work.
In other violence, NATO issued a statement saying its troops killed an Afghan man who failed to stop his vehicle as he approached their patrol in southern Helmand province Tuesday.
A roadside bomb in the same province killed five police officers and wounded four Tuesday, said Dawood Ahmadi, a spokesman for province's governor.
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.