Rebels in southern Colombia ambushed a military convoy on Wednesday, killing 10 soldiers in a hail of gunfire and explosions, authorities said.

The troops were traveling by truck on a remote jungle road in Putumayo state, one of Colombia's biggest cocaine-producing regions some 300 miles south of Bogota, when they came under attack, said Adm. Mauricio Soto, the Colombian navy commander.

Only one Marine in the convoy survived.

Soto blamed the attack on guerrillas of the Revolutionary Armed Forces of Colombia, or FARC, which has been battling to topple the government here for 40 years. The group funds itself through drug trafficking, kidnapping and extortion.

In February, the FARC launched some of its boldest attacks in two years on the military throughout the country, killing more than 50 soldiers and calling into question government assurances that the group was being weakened.

Also Wednesday, police said suspected FARC fighters attacked a squadron of US-supplied drug-fumigation planes and two escort helicopters in southeast Colombia, lightly damaging several of the aircraft and wounding a pilot.

The planes were spraying herbicides Tuesday over fields of poppy plants, the raw ingredients of heroin, near Algeciras, 160 miles southeast of Bogota, when they came under fire, a spokesman for Colombia's anti-narcotics police said.

At least one of the planes and the two combat helicopters escorting them were struck by gunfire or rockets but managed to fly back to their base safely, said the spokesman, who asked that his name not be used. A helicopter pilot was hit in the leg.

An aggressive fumigation program, paid for mainly by the United States, has resulted in a sharp drop in drug cultivation in Colombia since 2001. The program uses crop duster planes to fly over drug fields and spray the plants with herbicide.

The ferocity of the FARC attacks in the past two months has led many observers to question President Alvaro Uribe's claims that the rebels have gotten weaker since he ordered a costly military buildup upon coming to office more than two years ago.

Army officials maintain the FARC is made up of 12,000 fighters now, down from 18,000 a year ago, due to deaths, captures and desertions brought on by the government offensive.

(Chinadaily.com.cn via agencies March 24, 2005)