ISLAMABAD - Police in southwestern Pakistan say unknown gunmen Thursday shot and killed two female members of a polio vaccination team.

The assailants on motorbike opened fire on a team of health workers during a national immunization campaign just outside Quetta, capital of Baluchistan province, said senior police officer Naseeb Ullah.

The attackers, he added, fled the site of the attack and an investigation was underway to gather more information.

Rescue workers reported the slain health workers were a mother and her teenage daughter.

There were no immediate claims of responsibility for the violence. The shooting took place on the concluding day of the three-day national campaign to immunize children against the crippling disease.

Quetta, Pakistan Quetta, Pakistan Quetta, Pakistan

Pakistani Prime Minister Shahid Khaqan Abbasi condemned the violence.

“Polio teams are rendering a huge national service to save our children from the crippling disease. Attack on these dedicated workers, risking their lives for their nation, is an attack on our future,” Abbasi noted.

Attacks on polio teams are not uncommon in Pakistan. Militants perceive the immunization effort as part of a Western plot to sterilize Pakistani children.

In a bid to discourage the anti-polio campaigns in volatile areas, insurgent groups also propagate vaccinators indulge in spying on their hideouts.

Pakistan and Afghanistan officially were the only two nations across the globe to have reported 8 and 13 polio virus cases respectively in 2017, showing a historic dip in the number of cases in both countries, which share a long border.

Nigeria is the third country in the world with ongoing wild polio-virus transmission, but officials there reported no new cases in 2017.

Thursday’s attack on polio workers occurred just hours after militants killed two members of a Rapid Response unit of the provincial police in a drive-by shooting in Quetta. A third officer was seriously wounded, said police and hospital sources.

The outlawed Pakistani Taliban claimed it carried out the attack on police forces.