The Colombian government is insisting the leader of its largest rebel group, Manuel Marulanda, is dead, but is offering no proof to back up its assertion.
The allegation, contained in a statement by Admiral David Moreno, head of the general staff of the country's military, was followed by an announcement by President Alvaro Uribe, who insisted that some leaders of the Revolutionary Armed Forces of Colombia (FARC) were ready to free high-profile hostages such as French-Colombian politician Ingrid Betancourt.
"Manuel 'Shureshot' Marulanda, the main leader of the FARC, is dead," Moreno said, adding that the guerrilla died of still undetermined causes on March 26 at 6:30 pm.
His replacement as FARC leader will be Alfonso Cano, seen as the group's ideological leader, the military alleged.
The elusive Marulanda, who was about 80 when authorities said he died, founded the FARC over four decades ago. He has been rumored to be dead at least 17 times.
The rebel group has not commented on the announcement, but the military said that if the FARC were going to denied it, "they must prove it."
The statement said that Marulanda's death "would be the hardest blow that this terrorist group has taken, since 'sureshot' was the one who kept the criminal organization united."
Over 40 years, Marulanda turned a group of 48 armed farmers in southern Colombia into a thousands-strong organization which has fought the government and right-wing paramilitaries in a civil war that has claimed more than 200,000 lives.
The FARC has become South America's longest-running and largest insurgency. The rebels are believed to hold an estimated 750 people hostage, and traffic drugs to fund their insurgency against the government.
Meanwhile, Uribe said he had received "calls from the FARC in which some of the leaders announced their decision to leave the FARC and hand over Ingrid Betancourt if their freedom is guaranteed.
"The government's answer is 'yes, they are guaranteed freedom'" if they handed over hostages, Uribe said.
In a speech carried live on national television, Uribe said those leaders of the FARC who free the captives could be turned over to authorities from "France, so that they enjoy that freedom there."
The president also touted the government's offer to reward rebels up to a total of 100 million dollars when they turn themselves in alongside one or more hostages.
Uribe spoke from the town of Florida, in an 800-square-mile (2,050-square-kilometer) zone in the southwest which the FARC has asked to be demilitarized in order to negotiate a swap of high-profile hostages for jailed guerrillas.
The FARC have in their control Betancourt, a former Colombian presidential candidate who is both a Colombian and French national, three US nationals and dozens of Colombian police and military staff. They want to swap the hostages for some 500 imprisoned comrades including three in US jails.
Betancourt was seized by the FARC in 2002 while campaigning for the presidency, and has been held ever since. Pictures released in November showed her looking frail and the French government has warned that she may be gravely ill.
Last month French President Nicolas Sarkozy launched a "humanitarian mission" to contact FARC and obtain access to Betancourt, and sent a plane with doctors and diplomats to Colombia, but it was rejected by the rebels who said in a statement that they "do not act under blackmail."