The Revolutionary Armed Forces of Colombia (FARC) have released former governor Alan Jara, who had been held hostage by the guerrilla group since 2001.
It is also expected that regional deputy Sigifredo López, kidnapped in 2002, will be released in the next few days. Amnesty International has welcomed the news. On Sunday, the FARC released three police officers and a soldier.
"The release of the hostages, the police officers and the soldier is great news but the reality is that there are still many being held by the FARC and the ELN across Colombia," said Marcelo Pollack, Colombia researcher at Amnesty International. "Both guerrilla groups must urgently and unconditionally release all those civilians still being held captive."
The latest releases were facilitated by the International Committee of the Red Cross (ICRC), the Brazilian government and Colombian congresswoman Piedad Córdoba. They are the latest in a series of releases of high-profile hostages over the last year.
Amnesty International has reiterated that hostage-taking is a serious violation of international humanitarian law, which can constitute a war crime.
"Guerrilla groups must always treat humanely those they have captured, whether they are civilians or members of the armed forces. The humane treatment of anyone held by the FARC and ELN must never be made contingent upon the authorities complying with their demands," said Marcelo Pollack.
Over the last few years, there has been constant speculation that the FARC and the Colombian government were prepared to agree a "humanitarian exchange" - the exchange of FARC prisoners held by the Colombian authorities for hostages held by the guerrilla group.