The Colombian government has freed 16 Farc guerrillas as part of negotiations to end their decades-long conflict.
The rebels were released in a "goodwill gesture" in return for Farc's unilateral ceasefire in July, the government's peace negotiators said.
They are the first of a group of 30 to be pardoned.
Earlier this week, both sides asked for a UN mission to oversee the transition to peace, having set a March deadline to finalise a deal.
The mission of unarmed observers for a period of 12 months would guarantee that any ceasefire and disarmament would be genuine and permanent, they said in a joint statement at the peace talks in Cuba on Tuesday.
The freed guerrillas - nine men and seven women - had been serving prison terms for rebellion. The government said they had been pardoned on condition that they do not re-join the Farc (Revolutionary Armed Forces of Colombia).
Farc welcomed the move as a "positive gesture" but called on the government to also free 80 other rebels with health problems, the AFP news agency reports.
An estimated 220,000 people have been killed in the fighting between Farc and the Colombian military, which began in 1964. It is the longest-running armed conflict in the Western Hemisphere.
Since official peace talks started in Havana in November 2012, negotiators have reached agreement on key issues such as the political participation of the rebels, land rights, drug trafficking and transitional justice.
However it is unclear whether a final deal can be reached by the 23 March deadline set last year. The Farc said last week there were still "substantial hurdles" ahead.