Afghan officials say unidentified gunmen have killed three female polio vaccination health workers in the eastern city of Jalalabad, in what the United States' most senior diplomat in Kabul called "heartless" attacks.
Ghulam Dastagir Nazari, head of the immunization program at the Health Ministry, said the three women died in two separate shootings in Nangarhar Province’s capital.
The trio included two volunteers and one supervisor in the polio immunization program, Nazari said.
The official added that a blast also took place at the entrance to the health department for Nangarhar Province but left no casualties.
There was no immediate claim of responsibility for the attacks, which come a day after Afghanistan launched a new campaign to vaccinate millions of children across the country against polio, a highly infectious, water-borne pathogen.
Taliban spokesman Zabihullah Mujahid said the group had no role in the attacks.
U.S. Charge D'Affaires Ross Wilson said that "attacking vaccinators is as heartless as it is inexplicable."
"Today's murder of three polio campaign workers demonstrates a total disregard for human life. Such attacks are a direct affront to Afghans' dream of building a better life for their children," he tweeted.
Afghanistan and neighboring Pakistan, where insecurity and attacks by militants on health workers have slowed vaccination efforts, are the only two remaining countries in the world where polio is still prevalent.
Afghanistan has witnessed a rise in violence in recent months amid stalling intra-Afghan peace negotiations in Qatar, including targeted attacks on government employees, journalists, academics and rights workers.
Many of the killings have gone unclaimed, with Afghan and U.S. officials blaming the Taliban, which has denied involvement in many cases.
Earlier this month, three female employees of Enikass Radio and TV, a privately owned outlet based in Jalalabad, were killed in an attack claimed by the Islamic State extremist group.