Peshawar, February 18: At least one policeman was killed and two injured on Tuesday when an improvised explosive device went off near a police mobile van deployed for the security of polio workers in northwest Pakistan's Khyber Pakhtunkhwa Province, officials said.

This year's first nationwide polio vaccination drive began on Monday, aiming to vaccinate approximately 39.6 million children. The campaign involves nearly 265,000 polio workers going door-to-door to inoculate children under the age of five.

The incident took place in Kulachi area of Dera Ismail Khan city in the province where the van was deployed for the security of the polio workers canvasing the area, District Police Officer Wahid Mahmood was quoted as saying by the Dawn News.

One policeman was killed and the two injured have been shifted to the District Headquarters Hospital, where their condition is said to be stable, Mahmood said. The area has been cordoned off, while a search operation is underway, he added.

However, no group of the banned outfit has claimed the responsibility for the attack. Earlier this month, the National Institute of Health confirmed five more polio cases from Khyber Pakhtunkhwa and Balochistan province, bringing the tally for the current year so far to 17.

Last year, 144 cases were reported nationwide, 12 in 2018 and eight cases in 2017. Attempts to eradicate the crippling disease in Pakistan 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 polio workers are common in various parts of Khyber Pakhtunkhwa and Balochistan. This is one of the biggest hindrances to the eradication of polio from the country.

In January, two women polio workers were killed when unidentified assailants attacked a vaccination team in Swabi town of Khyber Pakhtunkhwa province bordering Afghanistan.

Last year in December, gunmen killed at least two policemen in an attack on a polio vaccination security team in Lower Dir district of the province. In January 2014, three workers were killed while in late 2012, five workers including four female workers were killed in Qayyumabad area.