Islamabad, Oct 29 (IANS): Armed men attacked policemen providing security for polio vaccination workers in Pakistan's Khyber Pakhtunkhwa province, killing a police officer and injuring another, police officials said on Tuesday.

The incident took place when a group of terrorists opened fire on the anti-polio team in the Dabori area of Orakzai district of the province, police sources in the area told Xinhua.

Police said that two terrorists were also killed in the ensuing exchange of fire between the security forces and the attackers, adding that the law enforcers have launched an operation in the surrounding areas to arrest those who fled from the scene of the combat.

No group or individual has claimed responsibility for the attack as yet, Xinhua news agency reported.

Earlier on Monday, Pakistan launched a nationwide vaccination campaign to inoculate more than 45 million children in various districts, according to a statement from the country's National Institute of Health.