A Pakistani mother and daughter were killed in the country's southwestern city of Quetta. There was no immediate claim of responsibility for the attack.
Pakistani officials said gunmen 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.
"Two terrorists riding a motorbike opened fire on the polio vaccinators in Shalkot area of Quetta city and killed two women health workers on the spot," Muhammad Sharif, a local police officer said.
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.
Prime Minister Shahid Khaqan Abbasi condemned the attack, ordering the concerned authorities to apprehend the culprits involved in the incident.
He also ordered the Balochistan government to provide comprehensive security cover to the polio teams.
Polio across Pakistan
According to the health officials, at least 84 people associated with the drive have been killed across Pakistan since December 2012.
Pakistan is among three countries in the world, including Afghanistan and Nigeria, where polio virus still exists and the country remains under a polio-linked travel restriction imposed by the World Health Organization (WHO).
In 2014, the WHO made it mandatory for all people traveling from Pakistan to carry a polio vaccination certificate.
During the last four years, Pakistan successfully brought the cases down from 306 in 2014 to 54 in 2015, 20 in 2016 and only eight cases in 2017, while no case has yet been reported in the current year.
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 sterilise Pakistani children.