One of the highest ranking women leaders of Colombia's main leftist guerrilla group has turned herself in after eluding capture for decades, officials said Monday.

Authorities say Nelly Avila Moreno, alias Karina, was one of the most violent female leaders of Latin America's longest-running insurrection.

Believed to be around 40 years old, Karina commanded the 47th Front of the Revolutionary Armed Forces of Colombia (FARC) until her surrender Sunday in the town of Argelia.

It is a further blow to the once-powerful guerrilla group, coming after a March 1 attack in Ecuador that killed Raul Reyes, the FARC's second in command, and the March 7 murder of Ivan Rios, one of the seven members of the FARC secretariat, betrayed by one of his fighters in exchange for a bounty.

Avila was allegedly behind four massacres carried out between 1994 and 1996 in the northwest Uraba region, as well as dozens of kidnappings and attacks on public officials.

"She was known for her cruelty and daring, and for the massacres and beatings she ordered over 20 years with the guerrillas. So she was a very important military target," Defense Minister Juan Manuel Santos said.

"She had become a legend, with the guts to carry out any action. Such people rise up rapidly through guerrilla ranks, and she had reached one of the most important posts of any woman in the organization," he added.

Former guerrilla fighters describe her as a "sort of Rambo" that would personally slit the throats of her enemies.

President Uribe had urged Karina to surrender in exchange for security guarantees, and had made her capture one of his top priorities in the government's fight four-decade fight against the FARC.

Santos said Avila would benefit from the country's formal demobilization program, adding she had come close to being captured several times during military operations during which she apparently lost an eye.

"We began to believe that she had nine lives like a cat," said Santos, adding that Avila had finally surrendered because "she was starving as she was surrounded and without food."

She also has also been linked to the 1983 murder of President Alvaro Uribe's father -- but speaking to reporters on Monday from a military base in Medellin Avila herself denied the rumors.

"I don't know and never knew who murdered the president's father," she said. "My hands are not stained by that incident."

The FARC has denied any involvement in the killing, and argued that Uribe's father was a "known drug trafficker" who could have been murdered by criminals.

Avila, who appeared visibly nervous, also denied being a "bloodthirsty" woman, as the government has portrayed her.

She also said she has had no contact with the leaders of her guerrilla unit since she was demoted to third in command in 2002.

Avila surrendered along with her male partner and a third fighter to Colombian intelligence service, with her teenage daughter acting as a "guarantor," officials said.

There were several reasons for Avila's surrender, authorities said, including a 1.5 million dollar bounty placed on her head.

Moreover, the FARC's 47th Front was "practically decimated," Interior Minister Carlos Hoguin said Monday in a television interview.

While at the height of her influence Avila had led some 350 guerrillas with the 47th Front, army intelligence estimates that the unit has now shrunk to a mere 50 fighters due to desertions and death.

The FARC is holding 39 top-ranking hostages, including Franco-Colombian former presidential candidate Ingrid Betancourt and three US contractors, who they want to swap for 500 imprisoned guerrillas.

Authorities believe that Avila was behind an attack in Jurado in December 1999, in which 25 soldiers died and 12 were taken captive.

Then in December 2005 she allegedly led an attack on police in northwestern San Marino which left eight policemen dead and 30 captive. They were later later released, authorities said.