The Taliban has murdered five women polio health workers in a series of attacks in Pakistan.
The victims were shot in the head at close range, two of them as they administered vaccine drops to young children.
The killings halted a polio campaign that international health officials say is vital to contain the crippling disease but which the Taliban claim is a cover for US spies.
The government is in the middle of a three-day vaccination drive targeting high risk areas of the country as part of an effort to immunise millions of children under the age of five.
Four of the women were gunned down in the southern city of Karachi, and the fifth in a village outside the north-west city of Peshawar. Yesterday a man working on the anti-polio campaign was shot dead down in Karachi. The Taliban also killed three soldiers in an ambush of an army convoy escorting a vaccination team in the north-west.
The attacks in Karachi were coordinated and occurred within 15 minutes in three different areas of the city that are far apart. In each case, the gunmen used 9mm pistols. Two of the women were 18 and 19, and the other two were in their 40s, he said. Two of the women were killed while they were in a house giving children polio drops. The other two were travelling between houses when they were attacked, he said.
Taliban opposition to the polio campaign grew last year after it was revealed that a Pakistani doctor ran a fake vaccination programme to help the CIA track down Osama bin Laden.
Janbaz Afridi, a senior health official in Khyber Pakhtunkhwa province, where the fifth woman was killed, said the shootings would not stop the local government from continuing its vaccination program in the province and the neighbouring tribal region, the main sanctuary for Taliban militants in the country.
"These incidents are depressing and may cause difficulties in the anti-polio drive, but people should not lose heart," he said. "The government is very serious, and we are determined to eliminate polio despite all odds and difficult conditions."
The shootings in Karachi all took place in areas mainly populated by ethnic Pashtuns. The Taliban is a Pashtun-dominated movement and many militants are reported to be hiding in these communities in the city.