More than 100,000 protesters have taken part in a peaceful march in southern India, chanting slogans against Prime Minister Narendra Modi's new citizenship law.

Saturday's protest, dubbed the "Million March", was organised by an umbrella group of Muslim and civil society organisations in Hyderabad city.

More than 40 percent of Hyderabad's estimated population of nearly seven million is Muslim.

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The Indian government has faced weeks of acrimonious and, at times, violent protests against the Citizenship Amendment Act (CAA), which was passed by Modi's government in December.

The Hyderabad protesters held placards reading "Withdraw CAA immediately" and "India's only religion is Secularism".

The new law eases the path for non-Muslim minorities from the neighbouring Muslim-majority nations of Afghanistan, Bangladesh and Pakistan to gain Indian citizenship.

But, if combined with a proposed national register of citizens, critics of the CAA fear it will discriminate against minority Muslims in India and chip away at India's secular constitution.

Modi's government maintains the new law is necessary to help minorities facing persecution in Muslim-majority nations, and it has called the pan-India protests politically motivated.

At least 27 people have been killed in protest-related clashes with police since early December.

Elsewhere, protests against the CAA also went ahead in several other Indian cities on Saturday with hundreds turning out in cities in the southern state of Karnataka.

Hundreds gathered at a rally in the tech hub of Bengaluru, with some accusing Modi's government of trying to divide India along communal lines, to distract from a sharp domestic economic slowdown and job losses.