One of Bollywood's leading directors called on three superstar actors to break their silence about a new citizenship law that has triggered riots in India, saying they could influence millions of fans.

At least 21 people have died since crowds took to the streets enraged by the Hindu nationalist-led government's legislation, which critics say discriminates against Muslims.

The violence and the political storm raging around it have posed a dilemma for a film industry that is dominated by Muslim actors, directors and crew but caters to India's broader, predominantly Hindu population.