Colombian rebels have released a video showing seven hostages, some held for nearly a decade, pleading for the government to talk to their captors.
The videotape was delivered to al-Jazeera's Colombia correspondent
The video of the captured police officers and soldiers is believed to have been filmed several months ago.
It surfaced a week after rebels said 11 kidnapped politicians were killed when troops attacked a guerrilla camp.
President Alvaro Uribe, who accused the rebels of murdering the men, is to lead anti-kidnap protests on Thursday.
In the video, which was delivered to Holman Morris, the Colombia correspondent of al-Jazeera and Radio France Internationale, the hostages urge the government to talk to the rebels and not attempt a military rescue.
One of the men, soldier William Dominguez, also tells how he had shared camps with the former presidential candidate, French-Colombian national Ingrid Betancourt.
She was kidnapped in 2002 along with her assistant Clara Rojas by guerrillas from the Revolutionary Armed Forces of Colombia (Farc).
"I ended up in a camp where there are more prisoners of war, with hostage politicians, like Ingrid, Mrs Clara and a boy who is always with them," Mr Dominguez said.
This may refer to a child Ms Rojas is believed to have had with one of her rebel captors.
Mr Dominguez said he and his fellow hostages are moved on an almost daily basis to avoid military attacks.
The father of soldier Pablo Emilio Moncayo, seized nine years ago, said the video was extremely distressing.
"This tears my soul apart, [to see him] in these conditions, so thin, poor boy and I unable to anything," he said.
Mr Moncayo has been walking across Colombia in chains in an effort to pressure the guerrillas and the authorities to reach an agreement to free the hostages.
Last week, the Farc said 11 politicians held hostage for five years died in crossfire during a military raid on a guerrilla camp in the Valle del Cauca region
The politicians' deaths have sparked anti-kidnapping protests
The Colombian government denied that any military operation had taken place in the area and accused the guerrillas of killing the men in cold blood.
On Tuesday, Mr Uribe condemned the rebels for refusing to release the politicians' bodies.
The rebels say they will not hand over the corpses until the military withdraws from the region.
However, news of the politicians' deaths has provoked revulsion across Colombia and nationwide protests, marches and church services are planned on Thursday to demonstrate against all kidnappings.
The European Union on Wednesday condemned the loss of life and called for a full and impartial investigation into the killing of the politicians. The EU also appealed for a new humanitarian agreement between the government and the rebels to ensure the safe release of hostages.
The Farc, which has been fighting the Colombian state for decades, is believed to be holding more than 50 hostages.
At the start of June, the Colombian government began freeing imprisoned rebels aimed at convincing the guerrillas to reciprocate.
But Farc leaders insist they will only discuss the possibilities of a prisoner exchange if and when the government grants a safe haven as a venue for talks - a request repeatedly rejected by Mr Uribe.