Police officials escorting Nazrul Islam (C) to court shortly after his arrest in June 2015

A court in India has sentenced a Bangladeshi national to life in prison for the rape two years ago of a nun in her 70s. The judge, who decreed that Nazrul Islam would never be released, said “the heinous crime deserves the strongest punishment”.

Five other men were jailed for 10 years for robbery during the assault.

The Mother Superior was raped in March 2015 at the Convent of Jesus and Mary school in the north-eastern state of West Bengal. The school is 30km from India’s border with Bangladesh.

The attack, which left the nun in a critical condition in hospital, was considered at the time to have been religiously motivated – Christianity is a minority religion in the state. The President of the State forum of Christian groups said then that the nun had previously appealed to police for security assistance after receiving threats.

According to the prosecution, six people were involved in robbing the school and ransacking the convent chapel. All six were also accused of gang rape but only Bangladeshi Nazrul Islam was found guilty.

Arnab Ghosh, a police superintendent, said: “At least two of them were armed and the rest were carrying burglary tools. In the chapel, a holy scripture was found torn and a bust of Jesus was broken.”

The police were criticised for perceived inaction after ten men were detained but no arrests made, despite the faces of some attackers being captured on CCTV. Islam, 28, was arrested in June 2015 and identified by the elderly nun in an identity parade.