New fighting erupted Friday in a southern Colombian jungle where dozens of soldiers and rebels have died in one of the most violent weeks in 35 years of guerrilla warfare.

President Ernesto Samper, in the war zone Friday, made an impassioned plea to industrialized countries to stop "selling weapons and buying the drugs that finance these belligerent acts of war and death."Military officers interviewed at an army base in the state capital, Florencia, confirmed that guerrillas are using the same modern weaponry as the army: machine guns, rifles, grenades, grenade launchers and shoulder-fired missiles.

The fate of 140 soldiers who clashed with rebels earlier this week remained unknown, said Maj. Juan Carlos Cardozo, an army spokesman.

Hundreds of army reinforcements attempted to penetrate the remote rain forest, but so far have been unable to evacuate the dead and wounded, said Cardozo. He confirmed new fighting in the area Friday, but no details were immediately available.

The Red Cross issued a statement urging the warring parties to cease hostilities and allow the relief organization to move in.

The rebels are stepping up their activities ahead of Sunday's congressional elections. About 100 guerrillas of the Revolutionary Armed Forces of Colombia, or FARC, set up a roadblock Friday on a highway near the southeastern city of Villavicencio, blocking passage to hundreds of vehicles and shooting a police officer to death.

Rebels were also suspected in a roadside bomb that exploded Friday alongside a vehicle carrying a congressional candidate in the northeastern state of Arauca. The candidate, Julio Acosta, escaped unhurt.

The rebels said 70 soldiers were killed and 30 wounded during a 24-hour battle Monday and Tuesday in the jungle region that is a center of Colombia's cocaine trade. In a statement Thursday, the FARC guerrillas said eight soldiers were taken prisoner in the region, 260 miles south of Bogota.

Families of the missing soldiers waited anxiously outside the Florencia base for word on their loved ones.

"They didn't give us any information at all," said a shaken Maria Emma Villanueva, whose 20-year-old son Jhon Freddy has not been heard from.