Police say gunmen shot to death a policeman protecting a team of female polio workers during a U.N.-backed vaccination campaign in a village of northwestern Pakistan.
Police officer Mohammed Nabi Khan says another police officer was wounded in Wednesday's attack in the district of Mardan in Khyber Pakhtunkhwa province.
He says no polio workers were harmed since they were inside a home giving polio drops to children at the time of the attack. No one immediately claimed responsibility for the attack.
In December, gunmen in separate attacks killed nine polio workers in different parts of Pakistan. Some Pakistani militants oppose the polio vaccination campaign, accusing health workers of acting as spies for the United States and claim the vaccine is intended to make Muslim children sterile.