Afghan President Hamid Karzai condemned as a "despicable act of terrorism" the slaying of two Afghan workers for aid agency World Vision who were shot by unknown gunmen in the west of the country.
"The enemies of Afghanistan, at the instructions of foreigners, kill those who are providing health care to the poorest communities throughout the country," Karzai said in a statement issued late on Monday.
Authorities have yet to identify the gunmen who shot an Afghan doctor and a driver for the international Christian relief and development organisation on Sunday after they delivered medicines to the town of Charsada in Ghor province -- a rare attack in a relatively stable region.
"This despicable act of terrorism was aimed at depriving the people of Afghanistan of their right to health care," Karzai said.
He did not identify the "foreigners" allegedly responsible.
Afghan officials often accuse eastern neighbour Pakistan of providing a haven for Taliban-led guerrillas who have stepped up their insurgency this year, often targeting government officials and aid workers.
Pakistan denies it, saying it does all it can to prevent cross-border infiltration by militants.
The murder of aid workers came as militants in another western province, Farah, staged a major attack on a district police headquarters late on Sunday and attempted suicide attacks, suggesting Taliban rebels were taking their fight from volatile southern provinces to the west of the country.