Marvelous Marvin Hagler, who dominated boxing's middleweight division in the 1980s -- and one of the toughest and most beloved boxers of the modern era -- died Saturday at the age of 66, according to multiple news reports on Sunday.

"I'm sorry to make a very sad announcement... my beloved husband Marvelous Marvin passed away unexpectedly at his home here in New Hampshire. Our family requests that you respect our privacy during this difficult time," Reuters quoted Kay Hagler as saying in a post on the Marvelous Marvin Hagler Fan Club page on Facebook.

No official cause of death was given. Boxing promoter Bob Arum and Top Rank later confirmed the news in a press release.

"Marvelous Marvin Hagler was among the greatest athletes that Top Rank ever promoted. He was a man of honor and a man of his word... He was a true athlete and a true man. I will miss him greatly," Arum said in remarks quoted by CBS Boxing.

Hagler was a member of the International Boxing Hall of Fame. He had a record of 62 wins, 3 losses, and 2 draws, with 52 knockouts.

His most memorable win was a three-round knockout of Thomas Hearns in 1985 that is considered as one of the most exciting bouts in Boston history.

"Marvin Hagler came to my fight in Boston. I appreciated what he said to me after my fight. Rest In Peace, my friend. Condolences to the Hagler family. Thank you, Marvelous Marvin Hagler, for all you gave to boxing," world-renowned boxing coach Freddie Roach said in a tweet.

"I'm crushed at the news that MARVELOUS MARVIN HAGLER has passed away! He was in his prime-POUND4POUND-the best, going 11yrs in 38 fights w/o defeat! He dominated the MW division 4 a decade!" boxing announcer Michael Buffer commented on Twitter.

Regarded as one of the great champions and the best pound-for-pound fighter in the sport, Hagler was knocked down just once in 67 professional bouts. He was selected as fighter of the decade in the 1980s.

Hagler married Kay Guarrera in 2000. He was previously married to Bertha Hagler from 1980-1990. The couple had five children.

Hagler lost to Sugary Ray Leonard in a highly-contested 1987 fight in Las Vegas. Upset, Hagler retired immediately at the age of 34 after the loss and moved to Italy, where he became an actor. He never returned to boxing since then.