Unknown gunmen attacked a two-woman health team administering polio vaccine to children on the outskirts of Peshawar on Tuesday, said local police officer Muslim Khan. “One woman died and the other sustained injuries in the shooting incident,” Mr. Khan said.

The United Nation’s World Health Organisation confirmed the casualties. “We condemn the attack in the strongest possible terms and the WHO has suspended its anti-polio activities in Peshawar until the security situation improves,” a UN official said on condition of anonymity.

Peshawar police said the two vaccinators who were shot had declined police escorts.

Authorities have been deploying security forces with the health teams in the vaccination campaign since December, when a series of shootings in different cities of Pakistan killed nine health workers.

The UN health agency, which partners with the government’s polio eradication drive, suspended its field work across Pakistan after the earlier attacks and now mainly assists with observers and assessment of vaccination drives.

Pakistan, Afghanistan and Nigeria are the only countries where the crippling polio virus still exists.