NEW YORK (AFP) — The shorts worn by Muhammad Ali in his legendary "Thrilla in Manila" boxing match are up for grabs at Sotheby's in New York, part of a growing sports memorabilia market eyed by auction houses.

Bids — including the latest for $3.8 million — have been rolling in since late March for the Everlast-brand shorts, which are white with black stripes and are signed by Ali.

The auction is open until 12 April.

The sale comes as Sotheby's is auctioning off a slew of sports lots, including a uniform from National Basketball Association (NBA) star Victor Wembanyama.

Despite a growing interest in historic sporting items, Sotheby's said that, as of Thursday, the minimum price agreed to by the seller of Ali's shorts has not yet been reached.

Sotheby's estimates the shorts could eventually fetch $4-$6 million.

Ali's 1975 "Thrilla in Manila" fight against Joe Frazier was held in the Philippines and followed his "Rumble in the Jungle" bout in the Democratic Republic of the Congo (then called Zaire) the year before.

Ali's fight in the Philippines went to 14 rounds before Frazier's coach threw in the towel.

"It was like death. Closest thing to dying that I know of," Ali said of the fight, which was held amid stifling heat and humidity, with temperatures heightened by TV lights.

Ali, born Cassius Clay in the southeastern state of Kentucky, is known as both a sporting great and for his role in fighting for civil rights for African-Americans. He died in 2016.

Also for sale is a raft of NBA jerseys, including French player Wembanyama's complete uniform from an exhibition game held earlier this year.

Interest in the game day goods also apparently extends to items from Wembanyama's locker — including a chair, water bottles and a towel.

For those who don't have the cash for the jersey — estimated to sell for $80-$120,000 — the locker contents are estimated to go for $5-$7,000.