Police say gunmen have fired on police officers protecting a team of polio workers in northwest Pakistan, killing one and wounding another.

Peshawar police official Naeem Khan Khattak says the two officers came under attack Saturday as they were returning to a police station after doing duty with the polio workers on the outskirts of the city, the capital of Khyber Pakhtunkhwa province.

No group claimed responsibility, but militants have killed more than a dozen polio workers and police protecting them over the last year in Pakistan.

They accuse health workers of acting as spies for Washington and claim the vaccine is intended to make Muslim children sterile.

Pakistan is one of only three countries where the virus is still endemic.