Former boxing champion Alexis Arguello, one of the best junior lightweights to step in the ring, was found dead at his home in Managua early Wednesday.
Nicaraguan presidential spokeswoman Rosario Murillo confirmed Arguello's death and an autopsy was pending. The La Prensa newspaper reported Arguello was found with a gunshot wound to the chest.
"We are upset," said Murillo, who declined to provide details about the death. "This is a heartbreaking announcement. He was the champion of the poor, an example of forgiveness and reconciliation."
The 57-year-old Arguello, who was elected mayor of Managua last year, retired after several comebacks in 1995 with a record of 82-8 with 65 knockouts.
Nicknamed "The Explosive Thin Man," Arguello was inducted into the International Boxing Hall of Fame in 1992.
In 1999, a panel of experts assembled by The Associated Press voted Arguello the best junior lightweight and sixth-best lightweight of the 20th century.
His popularity in his own country was so great that he carried the flag for Nicaragua at the 2008 Beijing Olympics, and led to his decision to seek public office.
Ran for mayor last November
Arguello fought against the Sandinista government in the 1980s after it seized his property and bank account, but later joined the party and ran for mayor of the capital last November.
He defeated Eduardo Montealegre, though opponents alleged the vote was fraudulent.
Arguello had returned Sunday from Puerto Rico, where he honoured the late baseball Hall-of-Famer Roberto Clemente.
His death prompted Nicaragua President Daniel Ortega to announce he was cancelling a trip to Panama for the inauguration of president-elect Ricardo Martinelli.
Arguello turned professional in 1968 and lost his first bout. He didn't lose much after that, and six years later rallied to knock out future Hall of Famer Ruben Olivares in the 13th round to win the WBA featherweight title.
He went on to win the super featherweight title and lightweight title, his five-foot-10-inch frame and long reach allowing him to move up in weight without losing his tremendous punching power.
At the time, he was only the sixth boxer to win titles in three weight classes, and was considered for a time the best pound-for-pound fighter in the world.
"Battle of the Champions"
Nobody had ever won titles in four divisions, and Arguello moved up in weight again in November 1982 to challenge junior welterweight king Aaron Pryor in a fight billed as "Battle of the Champions."
More than 23,000 fans packed the Orange Bowl in Miami, and the two waged an epic battle in which Pryor knocked out Arguello in the 14th round.
A rematch was ordered and they met again a year later at Caesars Palace in Las Vegas. This time, Pryor knocked out Arguello in the 10th round.
He announced after the fight that he would retire from boxing, but as so often happens in the sport, he couldn't stay away from the ring.
Arguello returned in 1985 to beat Pat Jefferson, and won another fight the following year, but didn't step into the ring again until 1994.
After defeating an unknown club fighter in Miami, Arguello lost to journeyman Scott Walker in January 1995 and retired for the last time.