Bengaluru, July 25: Boxing great Muhammad Ali's championship belt from his 1974 Rumble in the Jungle heavyweight title fight was bought by National Football League (NFL) team Indianapolis Colts owner Jim Irsaysold at an auction for $6.18 million.

Irsay, who owns the Indianapolis-based NFL team, has already amassed a huge collection of memorabilia.

It is worth recalling that he had bought Ali's shoes from the Thrilla in Manila in 1975 and Ali's robe from when he fought Sonny Liston in 1965, the first fight after he changed his name from Cassius Clay.

In a tweet, Irsay confirmed he acquired the belt for his collection of rock music, American history and pop culture memorabilia that is currently touring the country.

The belt will be displayed on August 2 at Chicago's Navy Pier and on September 9 in Indianapolis.

"Proud to be the steward!" Irsay tweeted.

"After several hours of watching two bidders go back and forth over this belt, this proved to be a battle worthy of the Rumble itself," Chris Ivy, Heritage's director of sports auctions, said in a statement.

"Two Muhammad Ali WBC belts are known to exist, one in a private museum collection unlikely to ever see the hobby's auction block. The only other known surviving Muhammad Ali heavyweight championship belt on Earth is presented here," the Dallas-based Heritage Auction said in its description.

"But the historical significance of the piece, arguably the most important boxing award ever made available at public auction, is quite simply immeasurable.

"Far more than just a trophy of elite athletic achievement, this belt serves as a mute witness to Muhammad Ali's undaunted pursuit of justice itself and as a symbol of the myriad complexities of race, religion and patriotism that challenge all of us to this day. It's a truly priceless artifact of the American experience and of an American life as consequential as any thus far lived," the Heritage Auction description added.

Fight of the century

The 1974 fight was one of boxing's most memorable moments. Ali stopped the fearsome George Foreman to recapture the heavyweight title in the African nation of Zaire.

Ali won the fight in a knockout in the eighth round.

The fight has been called arguably the greatest sporting event of the 20th century and was a major upset with Ali coming in as a 4-1 underdog against the unbeaten, heavy-hitting Foreman.

The fight is also famous for Ali's introduction of the rope-a-dope tactic.