The Revolutionary Armed Forces of Colombia (FARC) made the announcement in a statement on the Anncol news agency website.
"We announce the unilateral liberation soon of six prisoners," read the statement, giving no date.
The move is being made "as a gesture towards generating conditions favourable for a humanitarian exchange," euphemism for a swap of hostages for imprisoned FARC rebels.
"The conditions, time and place will be announced at the proper time," the statement read.
The release will take place in two stages: in the first stage the three police officers and the member of the military will be released, followed by the politicians Alan Jara, former governor of Meta province, and former deputy Sigifredo Lopez.
The leftist guerrillas have long wanted to swap 28 high-value hostages they are holding for some 500 imprisoned guerrillas held in Colombian and US jails.
The FARC, which has waged a four-decade battle against the government, is believed to be still holding hundreds of hostages in their jungle hideouts.
The hostages will be delivered to a committee headed by Senator Piedad Cordoba, who in the past has served as an intermediary with the guerrillas.
Jara was kidnapped in July 2001 when he was driving in a United Nations vehicle. Lopez is the last survivor of 12 deputies the FARC kidnapped in 2002.
The FARC was dealt a blow in July when commandos rescued 15 prominent hostages, including former presidential candidate Ingrid Betancourt - held for six years - and three US citizens.
Once a powerful well-armed movement of 17,000 fighters, the FARC has seen its strength diminish due to the death of top leaders and defections in its ranks.