Thousands in northeastern India protested on Monday against a proposal to grant citizenship to religious minorities in the region, except Muslims, with critics attacking the bill as prejudiced and a sop to Hindus before elections.

Protesters burned copies of the legislation in angry marches across Assam state, where millions have settled in recent decades after fleeing neighbouring Muslim-majority nations.

The controversial bill would grant citizenship to select groups — including Hindus, Christians and Sikhs, but not Muslims — who have moved from Bangladesh, Pakistan and Afghanistan and lived in India for at least six years.

The proposal has been hotly contested in Assam, a hilly state that has witnessed violence between settlers and indigenous groups, who say they have lost land and jobs to the newer entrants.

“This is just the first phase of our agitation,” said Palash Changmai, the general secretary of a student organisation that participated in a march.

“Today, we burnt copies of the bill and hoisted black flags in different towns and sub-divisions of Assam as a mark of protest.”

The legislation could be tabled in parliament as early as Tuesday, according to the Press Trust of India news agency.

The fiery opposition to the measure reflects the complex nature of religious and ethnic identity in Assam, a state already embroiled in a separate citizenship controversy.

A new registry of citizens compiled in Assam this year forced the state's 33 million people to submit documents proving they were there before 1971, when millions fled Bangladesh's independence war.

In July, a draft registry left four million people off the list, effectively rendering them stateless, drawing concern from human rights experts at the United Nations and rights groups.

But the new proposal, which would grant Hindus another path to citizenship in Assam, has been criticised for being prejudicial and comes as Modi, a Hindu nationalist, seeks re-election in national polls expected within months.

Critics say the bill, which offers preferential treatment to certain groups seeking citizenship, is a transparent pitch to voters as Hindu-majority India prepares for the world's largest election.

Assam, which is controlled by an alliance led by Modi's Hindu-right Bharatiya Janata Party, is known for its lush tea estates and rhino sanctuaries.

But for decades it has been plagued by violence between tribal and ethnic groups indigenous to the state and settlers from outside the region.