Indian police said Wednesday they have arrested four Bangladeshi nationals in connection with the rape of an elderly nun that sent shockwaves through the Christian community.

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 where she lived.

Deputy inspector general Dilip Kumar Adak said police tracked the suspects down to the northern state of Punjab after CCTV images and e-fit images were circulated nationwide.

"Four more Bangladeshi nationals resembling the photographs and sketches of the suspects in the rape and robbery at the Convent of Jesus and Mary High School in Ranaghat have been arrested," he said.

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

Adak said police had identified all eight people who broke into the convent using CCTV footage.

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