BOGOTA, Colombia (CNN) -- Days after the last government troops
                  departed from a small town in southeastern Colombia, hundreds of
                  armed guerrillas swept in aboard trucks and buses over the weekend in
                  advance of peace talks with government officials next week.

                  The 120 soldiers that left San Vicente del Caguan two days ago were the
                  last government troops to be pulled out of an area the size of Switzerland.

                  Leaders of the Revolutionary Armed Forces of Colombia (FARC) insisted
                  on the pullout before participating in the first peace discussions in six years.
                  The long-running civil conflict between the government and the oldest,
                  largest rebel group in the Western hemisphere has left some 35,000 dead in
                  the last 10 years alone.

                  The government had planned to leave the region by November 7, but
                  delayed the action, claiming some soldiers must stay for "logistical" reasons.
                  With 45,000 residents, San Vicente is the largest in the 16,000-square-mile
                  (41,000-square-km) demilitarized zone.

                  The town will open the negotiations on January 7.

                  "We have confirmed that the demilitarization is now total," said rebel
                  commander Joaquin Gomez on Saturday after combing San Vicente barracks
                  for signs of remaining troops and weaponry.

                  "The way is clear for the start of talks," said Gomez, head of FARC's
                   formidable Southern Bloc division.

                  As Gomez spoke, some 80 insurgents stood guard near the barracks and entrance
                  roads. Other guerrillas, broadcast on Colombian television, looked for lingering soldiers,
                  drove through San Vicente, and waved to townspeople from an open bus.

                  The troop withdrawal marks the first time in the 30-year civil war that the
                  government has agreed to guerrilla demands to leave such a large area.
                  FARC now has de facto political and military control of the region.

                  Critics worry that FARC will control the region like an "independent
                  republic," and use it to smuggle drugs out and weapons in. Yet FARC
                  maintains its negotiators cannot safely attend talks with military personnel in
                  the region.

                  Pastrana will attend talks

                  President Andres Pastrana is scheduled to open the negotiations in person.
                  He pledged to make peace a top priority when he took office in August.

                  Gomez, part of a proposed triumvirate of FARC negotiators, said he could
                  not confirm whether veteran FARC leader Manuel "Sureshot" Marulanda,
                  69, would take part in the talks.

                  FARC fears that extremist military factions and ultra- rightist
                  paramilitary gunmen are plotting to assassinate Marulanda, who has
                  built up the guerrillas from 50 to more than 12,000.

                  The rebel force have increasingly outwitted the military on the
                  battlefield the last two years, attacking army and police bases
                  almost at will. It now poses a threat to the stability of the entire region,
                  according to U.S. officials.

                  FARC has invited a number of international dignitaries to the start of the
                  peace talks, including Guatemalan President Alvaro Arzu and Nobel laureate
                  Rigoberta Menchu, the Colombian media reported. It remains unclear
                  whether any has accepted.

                  The demilitarization is scheduled to last until February 7. But political
                  analysts expect comprehensive negotiations will not take place in so short a
                  period on FARC demands. They include sweeping agrarian reform, an end
                  to unregulated free- market economic policies and a radical redistribution of
                  wealth.

                  The government has suggested it could extend demilitarization for at least
                  another three months.

                                 Reuters contributed to this report.