NEW DELHI — India's Supreme Court on Tuesday gave authorities in a northeastern state an extra month to complete a citizenship list to identify illegal immigrants in an exercise that has stoked concern for millions of people, most of them Muslim.

Residents of state of Assam, which borders Bangladesh, have to produce documents proving that they or their families lived in the country before March 24, 1971 — the year that hundreds of thousands of people fled Bangladesh during its India-backed war of independence from Pakistan.

"We extend the deadline for final publication of National Register for Citizens in Assam from July 31 to Aug. 31," chief justice Ranjan Gogoi said, adding that floods in Assam made work on the list difficult.

Millions of people have been displaced by the floods after torrential rains battered the region.

Work on the Supreme Court-ordered citizenship register has been going on since 2015 and a draft list published last year excluded more than four million of the state's residents, triggering widespread fears of deportation and jail.

Critics accuse Prime Minister Narendra Modi's Hindu nationalist-led government of using the citizenship exercise to further marginalize minority Muslims and bolster its support in the majority Hindu community.

Modi's Bharatiya Janata Party denies any bias but says it is opposed to the appeasement of any community.

Last week, the Modi government sought more time to compile the final list, saying thousands of people had produced fake documents to try to become Indian citizens.

Aman Wadud, a lawyer in Assam who is fighting cases for some of those declared illegal immigrants, said he hoped the extension would give authorities time to make the register "free, fair and credible". — Reuters