A nun in her 70s has been gang-raped by a group of raiders as she tried to prevent them from committing a robbery at a Christian missionary school in eastern India.

The nun was taken to hospital in serious condition after the attack by seven or eight robbers at the Convent of Jesus and Mary School in West Bengal state's Nadia district, investigators said. Officers are searching for the bandits who escaped with cash, a mobile phone, a laptop computer and a camera belonging to the school. The attack is the latest crime to focus attention on the scourge of sexual violence in India.