A policeman who was assigned to guard polio vaccination workers in Pakistan's Khyber Pakhtunkhwa (KP) province, was shot dead by unidentified gunmen, according to officials.

The miscreants riding on a motorcycle opened fire at the victim in the Kot Attal Sharif area of Dera Ismail Khan district on Monday, Xinhua news agency quoted a senior police official as saying.

The policeman was on his way to perform duties with an anti-polio team when he was attacked, said the official, adding that the attackers fled the scene afterwards, and a search operation is underway to arrest the culprits.

This was the third attack in two days on Pakistani policemen assigned to protect anti-polio workers in the province.

On Sunday, a police officer, who was returning home after security duty with polio vaccination workers, was killed by unidentified gunmen in Peshawar, the capital of KP province.

Similarly, another policeman was injured when a roadside bomb hit a police van escorting a polio vaccination team in the Ladha area of South Waziristan district later in the day.

According to government officials, Pakistan is one of the only two polio-endemic countries in the world along with its neighbour Afghanistan.