Despite sending army reinforcements to a southern province where FARC guerrillas have declared an ''armed strike,'' Colombia's government is having trouble regaining control.

BY STEVEN DUDLEY

ORITO, Colombia - Red and orange flames engulfed the 80-foot trees and rolled down a hill toward the small stream that passed through a hamlet. A plume of black smoke snaked toward the sky.

Celimo Solano said he ran from the nearby farm where he was working to see if his house had been caught up in the oil fire after leftist guerrillas blew up a 12-inch pipeline. It had not, but the rebels urged the 61-year old Solano and his wife to move away for their own safety.

The blast just one mile from an army base here underlined the difficult task the government is facing these days controlling the southern province of Putumayo -- a vast jungle region along the Ecuadorean border and long a bastion of FARC guerrillas.

Twelve days ago, the Revolutionary Armed Forces of Colombia units in the region declared an ''armed strike'' -- all commercial transport must stop, on threat of torchings -- in what appeared to be an attempt to lure more troops here and ease army pressures on the FARC in other parts of the nation. A half-dozen vehicles have been burned already.

DEPLOYMENTS

The army has sent in more than 1,000 troop reinforcements and several armored personnel carriers to help protect food convoys, but the massive deployments seem to have had little impact on the more mobile guerrillas.

Tomatoes and rice still line the store shelves, and the military flew in one planeload of supplies for civilians. But residents fear that this is only the beginning.

''If this goes another week we'll finish off everything,'' said Nidia Rosel, the 46-year-old manager of Supermercado Subasta in the oil industry town of Orito.

Rosel said she has already rationed sugar, and paid higher prices and risked losing merchandise to bring in other staples like potatoes. But she worries that the guerrillas may tighten the noose.

''Some people are moving around, but with caution,'' she said of the drivers of trucks, buses, and taxis not obeying the FARC's strike orders. ``[But] it's easier to find cowardice than bravery.''

Since the guerrillas declared the ''armed strike,'' they have also destroyed some of the region's oil pipelines and an oil well, and knocked out electricity -- forcing residents to live by candlelight after darkness falls. They also blew up an important bridge, forcing travelers to use a makeshift ferry.

Still not clear is why the FARC launched the attacks, with some rebel fighters saying only that the strike is designed to ''divert'' military pressures elsewhere.

Some speculate that the rebels are trying to relieve the pressure on a rumored army encirclement of a member of the FARC's high command, Raúl Reyes. Neither the military nor the guerrillas would confirm the accounts.

ARMY OFFENSIVE

Others believe it may be part of an effort to disrupt a two-year-old army campaign in southeastern Colombia, the center of FARC's activities for years. Known as Plan Patriot, the campaign by 17,000 troops has pushed the rebels deeper into the jungle outposts and greatly reduced their attacks on military bases and towns.

Government troops and police also have targeted Putumayo as part of a strong campaign to rid the province of its coca farms -- which in 2001 accounted for half of Colombia's production of the raw material for cocaine -- as well as the FARC.

A U.S.-financed herbicide spraying campaign has wiped out most of the coca farms. But just last month, fighters from the FARC's 48th Front attacked an army base in the Putumayo town of Teteye, killing 22 soldiers. ''The guerrilla war is very difficult to decipher,'' said Lt. Col. Francisco Javier Cruz, commander of the army battalion based in Orito. ``But the situation is under control, because we've been more on the offensive.''

This week, Cruz mobilized hundreds of troops toward guerrilla strongholds along the Ecuadorean border, where the army and the FARC have squared off along the Rumiyaco river.

Despite the heavy troop presence in their area, a unit of FARC fighters seemed largely unconcerned when journalists encountered them Wednesday near the river. They moved swiftly from hilltop to hilltop along jungle paths they could find even in the dead of night. When the army soldiers approached, they scampered off in small groups. Fighting soon ensued, and lasted through the next day.