Uribe wants more rebels to lay down their arms

The man, identified as Fidel Romero, said he had given himself up because he was tired of fighting a war that had no visible end.

He urged fellow fighters from the Revolutionary Armed Forces of Colombia (FARC) to turn themselves in.

Mr Uribe said last week that he believed the FARC - Colombia's biggest rebel group - was split between those who back political negotiations with his government and those who only want more violence.

The latest developments come as the government and the FARC are trying to reach agreement on a crucial element of any peace moves - the conditions for an exchange of prisoners.

Life as a fighter

Mr Romero, also known as Rafael Rojas Zuniga, was in charge of the FARC's 46th Front in the southern Santander department, Colombian media reported.

Addressing a news conference, he said he had spent 20 years as a guerrilla and had not been able to see his daughters for the past three years.

The decision to give himself up was "voluntary", he said, adding that he hoped other guerrillas would follow his example.

Defence Minister Martha Lucia Ramirez said all the necessary guarantees were in place for all those rebels who wanted to demobilise.

Mr Uribe came to power on a promise to crack down on the guerrilla groups who have waged a left-wing insurgency for nearly 40 years.

But during the recent Easter holiday, the security forces were unable to prevent rebel attacks and more than 20 people died in heavy fighting.

The BBC's Jeremy McDermott in Colombia said the rebels' aim was simple - to show Colombians that Mr Uribe's promises to restore order was a pipe-dream.