Indian Prime Minister Narendra Modi said on Tuesday he was "deeply concerned" about the rape of an elderly nun and the demolition of a church as protests for the better protection of women and religious minorities erupted across the country.

Shops and schools in a town in West Bengal state in eastern India, where the nun was raped, closed on Tuesday in protest over perceived police inaction, as anger mounts over the "inhuman" crime, business owners said.

Police have detained nine men for questioning but no arrests have been made in connection with the Friday attack, the most recent in a string of high-profile rapes in India.