Colombia's ELN rebels said Friday that military operations in one of their strongholds were endangering the life of a hostage and the prospects for stalled peace talks.
The warning came as President Juan Manuel Santos seeks to implement a peace deal signed Thursday with a larger rebel group, the Revolutionary Armed Forces of Colombia (FARC), and revive the aborted talks with the National Liberation Army (ELN).
Planned talks with the ELN broke down last month before they could start after the rebels failed to release hostage ex-congressman Odin Sanchez.
The guerrillas now accuse the army of putting Sanchez's life at risk by increasing operations in the jungle-covered department of Choco in northwestern Colombia, where he is being held.
"The increase in violent confrontations is endangering the process of freeing Odin Sanchez, preventing us from presenting proof he is still alive and putting his life at risk," the ELN said on Twitter.
They suggested that forces hostile to Santos within the army are seeking to "weaken the government and cause the ELN talks to fail."
The government earlier Friday demanded proof from the rebels that Sanchez is still alive.
Sanchez voluntarily went into ELN custody in April to take the place of his brother Patrocinio, who had fallen ill after three years in captivity.
Rumors of his death have swirled in recent days.
Santos won this year's Nobel Peace Prize for his efforts to end Colombia's half-century conflict, which has claimed 260,000 lives.
But tough opposition from hardline critics of both the newly revised FARC deal and the proposed ELN talks has cast uncertainty on the peace process.