Indian police have launched a massive manhunt to nab 15 people who allegedly gangraped at gunpoint four minor girls, all tribals, in the eastern state of Jharkhand late Sunday night, a senior police official said Monday. \"A major operation has been undertaken to track down the culprits who gangraped the four girls after abducting them from a hostel at Lawada village in the state\'s Pakur district. The girls are aged between 12 and 14 years,\" he said, on condition of anonymity. Gangraping is apparently becoming increasingly common in India. In December last year, a 23-year-old medical student was fatally gangraped by six men on a moving bus in the national capital. The case shocked India and sparked massive protests, forcing the government to bring in stricter laws to deal with sexual assaults on women.