(Reuters) - A group of Bollywood film makers, historians and citizens have written to Indian Prime Minister Narendra Modi urging him to stop mob attacks on minority Muslims and others at the bottom of society.

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Hindu mobs have targeted Muslims on suspicion of slaughtering cows they consider sacred as well as Dalits, the lowest group in the Hindu caste hierarchy, for being engaged in the cattle trade.

Upper-caste Hindus consider the cow to be a holy animal that should be revered, while lower caste Dalits and minority Muslims slaughter cows and consume beef for business and nutritional purposes.

“The lynching of Muslims, Dalits and other minorities must be stopped immediately,” the signatories said in the letter released to the media on Wednesday.

Among signatories of the letter were Anurag Kashyap, who is directing Netflix’s marquee show “Sacred Games”, and historian Ramchandra Guha.

Last month a Hindu crowd lynched a 24-year old Tabrez Ansari in the eastern city of Jharkhand, igniting nationwide protests.

Mobile phone videos shared on local television channels showed Ansari tied to a pole and begging for mercy as some men beat him with sticks and forced him to chant his devotion to Hindu gods.

Critics accuse Modi’s Hindu nationalist Bharatiya Janata Party of a deep-seated bias against Indian Muslims and say hardline groups allied to the BJP have become emboldened by his huge victory in the May elections.

Modi and his ministers have condemned the lynching incidents. The BJP denies any bias against Muslims though says it is opposed to the “appeasement” of any single community.

Modi condemned the Jharkhand incident in India’s parliament but film maker Aparna Sen, another signatory to the letter, said that was not enough. “It seems like the secular fabric of the country is slowly eroding and there comes a time where you feel you have to speak up,” she said.