Alfonso Cano, the top leader of the Revolutionary Armed Forces of Colombia, has been killed by Colombian troops during an anti-guerrilla operation, officials said.

Colombians rejoiced at the news, and hoped the biggest blow yet against Latin America's longest insurgency could herald an end to nearly five decades of war.

In a triumph for president Juan Manuel Santos' government, forces bombed a FARC jungle hideout in south-western Cauca region on Friday, killing several rebels.

Troops then rappelled down from helicopters to search the area, killing Cano in a gun battle a short time later.

Pictures of his dead body - with his trademark beard shaven off - were broadcast on television.

"The military has thus achieved one of its most important goals," Alberto Gonzalez Mosquera, governor of Cauca department, told local radio.

The death of the former student activist, who had a $US3.7 million bounty on his head, is unlikely to spell a quick end to a war that has killed tens of thousands in the Andean nation.

But it will further damage the drug trade-funded rebels' ability to coordinate high profile bombings, ambushes and kidnappings that have brought it worldwide notoriety.

"It is the most devastating blow that this group has suffered in its history," Mr Santos said in a brief televised address to the nation.

"I want to send a message to each and every member of that organisation: 'demobilise' ... or otherwise you will end up in a prison or in a tomb. We will achieve peace."

In one road on the outskirts of Bogota lined with bars and restaurants, revellers spilled into the street, dancing and chanting with joy: "Cano is dead!"

The death of Cano, 63, who took over leadership of the rebels after FARC's founder died in 2008, is a major strategic victory for Mr Santos, who came to office last year promising to keep up a hard-line stance against the guerrillas.

It will ease the pressure he has been under over a recent upsurge in small-scale attacks, and will also reassure investors in the booming oil and mining sectors.

Cano's death followed the killing last year of one of his main henchmen, Mono Jojoy, in a bombing and raid of his camp.

Cano's real name was Guillermo Leon Saenz Vargas.

Guerrilla force

The FARC is Colombia's oldest and largest guerrilla force, believed to have some 8,000 members. The leftist group has been at war with the government since its founding in 1964.

It began its campaign of kidnappings in the mid-1980s and army hostages were to serve as bargaining chips for FARC prisoners.

By the late 1990s more civilians and political leaders were being snatched as well, winning the group greater notoriety but also increased influence with its government interlocutors.

The FARC suffered a serious loss in 2008, when its number two man, Raul Reyes, died during a Colombian raid in Ecuadoran territory.

Reyes was killed in an air raid that was followed by a Colombia army ground operation that left numerous guerrillas dead.

That raid led to a major diplomatic rift between Colombia and Ecuador, and for a while appeared to bring Latin America to the brink of regional war, after troops were mobilised by Venezuela and Ecuador.

That same year, the FARC also lost its founder and revered leader, Manuel "Sureshot" Marulanda Velez. The reclusive 80-year old rebel chief, who was last seen in 1982, died in March 2008 after a brief illness.

In recent years, the Colombian government has taken a hard line against the FARC, which has answered in kind.

It flexed its muscle during former president Alvaro Uribe's August 2002 inauguration, when the group bombed the presidential palace, killing some two dozen people.

Reuters/AFP