Unidentified gunmen shot dead a policeman escorting a team of polio workers in northwest Pakistan on Tuesday, a day after a nation-wide campaign was launched against the crippling disease still endemic in the country.

Several school students in Pakistan's Khyber-Pakhtunkhwa province reportedly fell ill and were taken to hospital on Monday after being given anti-polio drops during a country-wide campaign aimed to administer anti-polio drops to 39 million children under five years of age.

Pakistan is one of the three countries, along with Afghanistan and Nigeria, where polio is still endemic.

On early Tuesday morning, the unknown gunmen opened fire at Assistant Sub Inspector of police Imran Khan who was escorting a polio team, police said.

The team was administering oral polio drops to children at Bacha Khan Chowk in Bannu district bordering north waziristan district in Khyber Pakhtunkhwa province, they said.

The gunmen fled from the scene after killing the policeman on duty, police said.

More than 260,000 polio workers have been deployed to administer anti-polio vaccines to children in all four provinces of Pakistan,as well as Pakistan-occupied Kashmir and Gilgit-Baltistan.

Despite efforts, Pakistan has not been able to completely eliminate polio. Six cases of polio have been reported so far in 2019. Twelve cases were reported in 2018 and eight in 2017.

Attempts to eradicate the crippling disease have been seriously hampered by deadly targeting of vaccination teams in recent years by militants, who oppose the drives, claiming the polio drops cause infertility.

Attacks on immunisation teams have claimed 68 lives since December 2012.

Earlier this month, member of a polio monitoring team was gunned down on Monday by a man after a verbal brawl during a campaign at a village near Pak-Afghan border.

In January 2014, three workers were killed while in late 2012, five workers including four female workers were killed in Qayyumabad area in Karachi.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)