Indian police have arrested four Bangladeshi nationals in connection with the rape of an elderly nun.

The nun, who is in her 70s, needed surgery after she was attacked last month when a gang of robbers broke into the convent school in the eastern state of West Bengal.

Police tracked the suspects down to the northern state of Punjab after CCTV images and e-fit images were circulated nationwide.

Two other suspects in the case are already in custody after they were arrested last week.

One had been hired by the nuns to do construction work.