Military jets flew hundreds of sorties against a major rebel stronghold Thursday, bringing Colombia's 38-year civil war into a potentially bloodier phase after the peace process was abruptly halted.

Bombs began falling on rebel territory just hours after President Andres Pastrana — angered by a rebel hijacking of a civilian airliner — broke off peace talks and condemned the rebel Revolutionary Armed Forces of Colombia, known by its Spanish initials, FARC.

The government ordered 13,000 troops to advance on the rebel stronghold, and three planeloads of counterinsurgency troops landed at an airport in Florencia, a three-hour drive to the west.

Army officials said 85 targets were hit in more than 200 sorties against the rebel safe haven, a Switzerland-sized area of pasture and rainforest that was the site of the peace negotiations. The government did not comment on casualties, but there were unconfirmed reports that the aerial bombardment hit the tiny hamlet of Rubi.

Late Thursday, State Department spokesman Richard Boucher said the United States "understands and supports" Pastrana's decision to suspend peace talks with the rebels.

"We've always expressed our support for President Pastrana," he said. "We've always said these are decisions for him to make."

A woman reached by two-way radio in Rubi said a boy about 4 years old and an adult were killed, and four people were wounded. The woman, who gave her name only as Adriana, pleaded for medical supplies. Officials in San Vicente del Caguan, the rebel zone's main town, said they would try to send an ambulance at daylight.

The warplanes' targets included clandestine airstrips and rebel training camps in the safe zone, which Pastrana ceded to the FARC in November 1998 in an effort to bring the 16,000-strong rebel army to the negotiating table. The rebel haven in southern Colombia is sparsely populated, with about 100,000 people.

A jet fighter was hit by guerrilla ground fire but was not seriously damaged and returned safely, Air Force chief Gen. Hector Velasco said.

A top army commander predicted a bloody fight, but there were no signs that military troops had yet entered the zone.

"It's dicey, and we will surely suffer casualties, but we have a moral obligation to win this war," Gen. Euclides Sanchez told Caracol Radio.

Residents in San Vicente del Caguan posted white flags at their homes.

"The white flags symbolize peace. We don't want anything to happen," said Amelia de Ficaro, 68.

Residents stripped six vehicles abandoned by the rebels along a road outside town. Also left behind was a sign that referred to U.S. anti-drug aid to Colombia: "The gringos give the arms. Colombia provides the dead." Some 3,500 people are killed annually because of the war.

A rebel in camouflage and brandishing an AK-47 rifle manned a checkpoint outside San Vicente del Caguan.

"We'll keep patrolling because this is Colombia and we're all over Colombia," he said. He waved through journalists, wishing them "Feliz viaje" — happy trip.

On the road further outside the zone, an Associated Press team saw a 60-year-old woman get shot in the leg when a bullet fired by a FARC guerrilla ricocheted off a truck's tires. The rifle-toting rebel, who was trying to immobilize the truck to block traffic on the road, fled.

The FARC did not comment on the offensive.

Late Thursday, an electrical power station was dynamited in Altamira, in southwest Huila State, north of the FARC territory. Technical crews were evaluating the damage, local power company president Julio Gomez said. No group has been accused in the attack.

Phone lines to rebel headquarters were cut shortly after Pastrana condemned a rebel hijacking of a civilian airliner Wednesday. Guerrillas released the 29 crew members and passengers, but kidnapped a senator, despite FARC pledges to seek a cease-fire by April.

Many Colombians rallied around Pastrana, whose peace policy had been highly unpopular.

"Colombia was generous with the guerrillas, but now there is no way to continue this process," said Sabas Pretelt de la Vega, a top business leader.

"We should have done this a long time ago," said Army Cpl. Carlos Vanegas, standing guard on a highway leading to the rebel zone.

"Everybody is tired," said Samuel Dominguez, a cheese vendor in Bogota. "Now we have to accept that we are at war and confront it. Hopefully, we will win."

Pastrana told reporters he still supports a negotiated solution but could not foresee more talks until the FARC demonstrates a sincere desire to achieve peace. He said he decided almost immediately after the hijacking to break off negotiations.

"The truth is, we don't understand why they did it," Pastrana said.

U.N. Secretary-General Kofi Annan offered his "good offices" to find a political solution and called on all forces to spare civilians. Amnesty International and Human Rights Watch urged the government to prevent right-wing paramilitaries from entering the zone and killing civilians suspected of collaborating with the rebels.

U.N. peace envoy James LeMoyne, who got the two sides to agree to cease-fire talks last month, expressed concern for the safety of residents in the zone.

The escalation comes as Washington is considering expanding training and equipment deliveries to the Colombian military. At any given time, there are about 250 U.S. military personnel, 50 civilian employees and 100 civilian military contractors in Colombia.

Sanchez said none were participating in Thursday's offensive.

The U.S. government has limited its military aid to counternarcotics operations but also has labeled the FARC a terrorist organization — leaving open the possibility it could provide aid to fight the group. The Bush administration has asked Congress to authorize $98 million to train and arm a Colombian army brigade to protect an oil pipeline.

Speaking to reporters Thursday, Pastrana urged Washington to allow its military aid to be used against the guerrillas.

"We hope we will be able to use all of these tools," he said.

Colombia's war pits the FARC and a smaller rebel group, the National Liberation Army, against government troops and an outlawed paramilitary militia.