Pakistani officials say gunmen have shot and killed a mother and her daughter who were taking part in an anti-polio campaign in the southwestern city of Quetta.

Local police official Naseeb Ullah says Thursday’s attack took place when hundreds of polio teams were vaccinating children to save them from the crippling disease. The attack took place days after Pakistan launched a campaign against polio across the country.

Rescue officials say the slain workers were a mother and her daughter.

There was no immediate claim of responsibility.

Pakistan, Afghanistan and Nigeria are the only three countries in the world where polio hasn’t been eliminated.

Pakistan regularly launches anti-polio drives despite threats from the Taliban, who perceive the campaign as part of a Western conspiracy and claim it will sterilize Pakistani children.