The escaped Colombian congressman held hostage by Marxist guerillas for eight years kept himself sane by delivering lectures to imaginary students, he has revealed.

Speaking the day after he emerged from the jungle with the rebel chief who escaped with him, Oscar Tulio Lizcano said loneliness was his main enemy during his years as a prisoner of the Revolutionary Armed Forces of Colombia (FARC).

Banned from speaking even to the lowliest of the rebels, he found the isolation at times unbearable.

"I was so lonely," he told AP. To keep his mind occupied, the 62 year old economist placed sticks in the ground and pretended they were his students.

"I gave them names and they were my students," he said. "I gave lectures that I prepared, in history (in themes such as) the First World War, anecdotes from (Simon) Bolivar and philosophy."

He also passed the time reading, listening to the radio and occasionally playing chess with his captors.

Dr Lizcano and the rebels' young commander, Wilson Bueno, crept out of the guerillas' camp on Thursday night. Walking only at night and hiding during daylight hours, they struggled through the jungle for three days before reaching an army post near the town of San Jose del Palmar on Sunday.

But when he tried to attract the attention of soldiers, said Dr Lizcano, they thought the bedraggled man screaming at them from across a jungle river was a drunk, and they ignored him.

It was only when the haggard escapee lifted the Mr Bueno's Galil assault rifle as he leaned on his shoulder, that the soldiers realised the two men were escaping from the rebels.

"They jumped in the river and then I started to shout, 'I'm Lizcano,'" he said, speaking from a clinic in the western city of Cali where he is being treated for anaemia and poor nutrition.

During their arduous trek, with no food and no sleep for 72 hours, Dr Lizcano said he was in such a weak state that he told Mr Bueno, 28, who is also known by the alias Isaza, "I can't make it, save yourself,.

"He said, 'No, no way. I want to leave here with you,' " he said. "He took me by both hands, almost dragged me". A long time before they fled together, he added, the rebel chief had told him that his family was indebted to the congressman for helping them get housing in the 1990s.

Dr Lizcano was abducted on August 5, 2000, in the village of Riosucio in Caldas prince, northwest of the capital, Bogota. At the time he was a Conservative Party congressman.

He is the first hostage of FARC to gain freedom since the rescue on July 2 of Ingrid Betancourt, the French-Columbian presidential candidate, and three Americans. It is also the first time a FARC fighter has deserted with his hostage

Since Ms Betancourt's rescue four months ago, he said, the rebels marched him through the jungle every day with 14 guards, seven men and seven women.

The clinic treating Dr Lizcano said he was suffering from anaemia due to his poor nutrition, and infections from parasites but that his heart, lung and brain function appeared normal.

Mr Bueno was reunited with his girlfriend, who had fled the rebel column in June, and with his family in Pereira.

President Alvaro Uribe said Mr Bueno and his girlfriend would be rewarded with cash and asylum in France. Late last year, France offered asylum to FARC rebels who demobilise as part of an effort to secure the release of hostages.

Juan Manuel Santos, the Defence Minister, said Mr Bueno would receive a $US419,000 (£272,218) reward. The young man had told him he had been a guerilla since he was 12 years old, he said.

The army commander in Periera, Colonel Emiro Barrios, said the rebel had told him he decided to desert with Dr Lizcano because of the isolation, fatigue and hunger he suffered in the last few months as the army blocked supply routes to the column.

FARC still holds at least 20 politicians, police officers and soldiers, some of whom have been prisoners for more than a decade.

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