Colombia's embattled FARC guerrillas on Sunday handed over four political hostages, with two more captives set to be released later this week.

The hostages -- part of a group of six hostages the Marxist rebels have promised to free by Wednesday -- landed by helicopter in Villavicencio, 90 kilometers (56 miles) southeast of Bogota, around 7:00 pm (0000 GMT).

Policemen Alexis Torres, Juan Fernando Galicia and Jose Walter Lozano, and soldier William Rodriguez were greeted at the terminal by Colombians for Peace, the group that helped broker the handover.

The fate of the hostages and members of humanitarian delegation that received them had been uncertain for several hours, after a member of the delegation told Venezuelan television that the hostages' arrival was delayed due to Colombian military operations in the area where they were freed.

However, Colombia's High Commissioner for Peace, Luis Carlos Restrepo, dismissed the assertion, telling reporters: "We will not allow people to launch unfounded accusations."

Venezuela's Telesur also reported that a rebel from the Revolutionary Armed Forces of Colombia (FARC) was killed in clashes with the Colombian army during the rescue operation, citing a spokesman for the insurgent group.

The International Committee of the Red Cross (ICRC) had previously secured a commitment from the country's defense minister to halt military operations in the Caqueta province, paving the way for the humanitarian mission.

The four hostages were received in the southern province of Caqueta by a delegation that included Senator Piedad Cordoba, representatives of the ICRC and members of Colombians for Peace.

Cordoba played a key role in talks to secure the hostages' release, a unilateral move that has marked an about-face for the rebels who had previously ruled out freeing captives without concessions.

The same helicopter that retrieved the four hostages was to due to pick up on Monday Alan Jara, a former governor abducted in 2001, in a similar operation. The rebels were expected to release on Wednesday former lawmaker Sigifredo Lopez, kidnapped in 2002.

Once all six hostages are released, the FARC rebels, who currently hold between 350 and 700 hostages, will only hold 22 "political" hostages. Jara and Lopez are the last politicians held by the group.

Colombians for Peace, said it would ask the guerrillas to undertake more humanitarian gestures as part of a written dialogue with the rebels that began in September.

"We are going to continue on the path of a written dialogue that is based on humanitarian acts," said Ivan Cepeda, one of the group's leaders.

In a statement posted online, the FARC had promised on December 21 to release the hostages.

The group has described the move as a "goodwill" gesture, while the Colombian government has called it a "maneuver" designed to ease military pressure and gain international sympathy.

The release reverses a FARC decision announced in early 2008 to stop handing over hostages without a demilitarization of certain regions.

The captives are part of a group of so-called "political hostages" the FARC has wanted to swap for some 500 guerrillas held in Colombian and US jails.

The rebels last carried out a unilateral release of hostages in January and February 2008.

In July, French-Colombian Ingrid Betancourt -- a former presidential candidate -- was rescued in an operation mounted by Colombian spies who tricked the rebels into handing her over along with 14 other hostages.

Former Colombian lawmaker Oscar Tulio Lizcano managed to escape his captors in October.

The FARC -- Latin America's oldest and most powerful guerrilla force -- has been trying to topple the Colombian government since the 1960s. A humanitarian prisoner swap has been considered for several years with the rebels.