Islamabad, Feb. 19 -- A policeman was killed in firing by unknown gunmen in Pakistan's northwest Khyber Pakhtunkhwa (KP) province, police officials said on Wednesday.

According to the police officials, some unknown armed persons attacked the polio vaccination team in the Bajaur district of the province.

Police added that the team was engaged in a door-to-door vaccination campaign to give polio drops to children when the attack happened.

The assailants fled the scene after carrying out the attack, and a search operation is underway to arrest the culprits, said the police.

Following the incident, a heavy contingent of police reached the area. Security forces cordoned off the area and launched an investigation into the attack.

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