BARRANCABERMEJA, Colombia (AP) -- In night tinged orange by flames
                  flaring off a huge oil refinery, rightist gunmen are methodically killing
                  suspected rebels and their sympathizers in an unprecedented urban offensive in
                  Colombia's oil center.

                  The victims show up most mornings along streets or in grassy gullies. They
                  are typically young men shot five or six times in the head -- a trademark,
                  officials say, of the United Self-Defense Forces of Colombia, known as the
                  AUC.

                  Already this year, police have recorded nearly 200 homicides, compared with
                  570 for all of last year.

                  The landowner-backed AUC previously operated mostly against rural villages.
                  But the group is now believed to control about 80 percent of the neighborhoods
                  of Barrancabermeja, a city of 300,000 people that processes three-fourths of the
                  country's petroleum and was for decades a guerrilla stronghold.

                  Should the city fall completely into the hands of the rightist gunmen, some
                  observers fear the city could become a thorn in peace talks and a foothold for
                  the paramilitaries to expand their power and influence nationwide.

                  "The paramilitaries could become a bigger threat to Colombia's stability than the
                  guerrillas," said the regional army commander, Gen. Martin Carreno.

                  The most recent wave of killings -- including the
                  assassination of a labor leader dragged from his
                  home at night and shot several times in the head
                  -- comes as the AUC opposes government plans
                  to cede a safe haven in two nearby towns to the
                  leftist National Liberation Army.

                  The Rev. Francisco de Roux, who is active in
                  peace efforts here, believes the AUC could easily
                  sabotage planned peace talks in the haven, which
                  is an hour's boat ride up the Magdalena River
                  from Barranca, as residents call their city.

                  "This is the most difficult moment in the history
                  of Barranca," said Antonio Navarro, a Colombian
                  congressman who has scheduled hearings on the
                  situation. "My impression is that the paramilitaries
                  have already taken control."

                  The city's violence is drawing international attention.

                  "This city needs to be freed, freed from the guerrillas and freed from the AUC,"
                  U.S. Sen. Paul Wellstone, a Democrat from Minnesota, said recently while
                  touring a soup kitchen run by the Popular Women's Organization.

                  The group has been declared a "military objective" by the AUC because it does
                  social work in rebel neighborhoods.

                  A woman who had been slicing onions and cabbage for the day's lunch said
                  that moments before Wellstone and U.S. Ambassador Anne Patterson arrived on
                  March 24, a man scaled a wall behind the building and pulled a gun on her.

                  The intruder, believed to be a paramilitary member, grabbed her
                  kitchen knife, cut open her blouse and shoved her, said the frightened cook,
                  declining to give her name. Before leaving, the man demanded she reveal the
                  whereabouts of families who had sought refuge with the women's organization.

                  "I'm sorry this happened to you," Wellstone, a critic of growing U.S. military aid
                  to Colombia, told the woman, whose blouse was held together by a safety pin.
                  "The AUC should not be able to do this with impunity."

                  The assault on Barranca follows AUC advances in smaller towns and villages
                  throughout a large northeastern region along the Magdalena River that was the
                  cradle of the National Liberation Army, Colombia's second-largest guerrilla
                  group.

                  The AUC first stormed into a poor Barranca neighborhood in May 1998, killing
                  seven people at a street fair and taking 25 others away in trucks. The prisoners
                  were "tried" as rebel sympathizers and executed, the AUC later announced.

                  Such massacres have now given way to selective assassinations, with rebels
                  themselves taking part in the slaughter, officials and human rights monitors
                  said. Offered guns, cell phones and a $250 monthly salary -- more than they
                  ever earned as guerrillas -- dozens of rebels have defected to the paramilitaries
                  and identified former comrades.

                  In addition to grabbing enemy territory, the paramilitaries are reportedly
                  muscling in on a multimillion-dollar trade in contraband gasoline, "taxing" gangs
                  that punch holes in pipelines and sell the fuel in Barranca's back alleys.

                  Increased police and army patrols in the neighborhoods covered with rebel
                  graffiti and murals of Cuban revolutionary hero Che Guevara have been unable to
                  stem the AUC onslaught. But police and military officials deny charges that they
                  are turning a blind eye or working with the paramilitaries.

                  "I could go into a neighborhood where 20 guys are playing soccer and they all
                  might be paramilitaries, but I can't arrest them if residents are too afraid to testify
                  against them," said Barranca's police commander, Col. Jose Miguel Villar.

                  Copyright 2001 The Associated Press.