In the days before the rape of an elderly nun in an armed assault that has shaken India, death threats and extortion attempts had already shattered the peace at her Convent of Jesus and Mary school, police and school officials say.

For 19 years, the Catholic school in the town of Ranaghat in West Bengal state had been teaching children of workers at a nearby jute factory without incident. But three weeks ago, the school received death threats and demands for money in anonymous phone calls just days after the nuns had an altercation with the father of a boy who was expelled.

The attack also comes amid a trend of worsening security for India's Christian minority, less than one year since the government of Hindu nationalist Prime Minister Narendra Modi came to power.