Gunmen shot and killed a mother and her daughter who were working for an anti-polio campaign underway in Pakistan's southwestern city of Quetta on Thursday, police said.

The attack took place as hundreds of polio teams were vaccinating children against the crippling disease, police official Naseeb Ullah said.

Pakistan this week launched a drive against polio across the country.

In a separate attack in Quetta, the capital of Baluchistan province, assailants killed two policemen.

Prime Minister Shahid Khaqan Abbasi condemned the attacks. There was no immediate claim of responsibility for either attack.

Pakistan, Afghanistan and Nigeria are the only three countries in the world where polio is endemic and has not been eliminated.

Pakistan's government 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.