(Adds Karzai comments, paragraphs 11-13)
By Sayed Salahuddin
KABUL, Aug 13 Suspected Taliban insurgents killed three female aid workers and their Afghan driver in an ambush on Wednesday, officials said, the bloodiest single attack on foreign humanitarian workers in Afghanistan in recent years.
Rising violence has already forced aid agencies to restrict humanitarian work at a time when drought and high prices are putting more people under pressure.
The three women, a British-Canadian, a Canadian and a Trinidadian-American, worked for the U.S.-based International Rescue Committee (IRC) and were ambushed as they were travelling north towards Kabul through the province of Logar.
"We are stunned and profoundly saddened by this tragic loss," said George Rupp, president of the IRC in the statement.
"Words are inadequate to express our sympathy for the families and loved ones of the victims and our devoted team of humanitarian aid workers in Afghanistan," he said.
Abdullah Wardak, the governor of Logar province, said the women and their driver were chased by gunmen in a Toyota Corolla car who then opened fire on their vehicle.
The U.S.-based IRC's work in Afghanistan focuses on providing returning refugees with shelter, water and sanitation, and developing the health care system.
But the agency has now suspended all its humanitarian aid programmes in Afghanistan indefinitely, the IRC said.
Aid agencies this month complained that rising violence was hampering their work and said 19 Afghan NGO staff had been killed this year.
Three district IRC offices have been attacked and destroyed since March, the IRC Web site said. Two Afghans working for IRC were killed in an ambush, also in Logar province, in July 2007.
Afghan President Hamid Karzai described the attack as unforgiveable.
"It is not in our culture to kill women, Afghans never kill women," Karzai said in a statement.
"This unforgivable incident, without any doubt, was carried out by the enemies of Afghanistan, by non-Afghans."
The United Nations condemned the ambush and said that all sides in the conflict must recognise the neutrality of humanitarian workers.
Violence has surged in Afghanistan this year with more clashes in each of the past three months than in any month since U.S.-led and Afghan forces toppled the Taliban in 2001. (Reporting by Sayed Salahuddin; Editing by Paul Tait)