India, Feb. 4 -- A policeman was killed after unidentified gunmen opened fire on a polio vaccination team he was guarding in northwest Pakistan's restive Khyber Pakhtunkhwa province, police said on Tuesday. The incident occurred on Monday in Mirali tehsil of North Waziristan district bordering Afghanistan. The assailants managed to flee from the scene after the attack. Police contingent rushed to the site and cordoned off the entire area. A search operation was launched in the area. Polio workers in Pakistan and their security escorts have faced repeated attacks over the past decade, particularly in parts of Khyber Pakhtunkhwa and the former tribal districts.Despite these threats, the government continued nationwide polio drives under str...