Army units backed by helicopter gunships chased leftist rebels into a mountainous area south of Bogota today, a day after the heaviest fighting in months between troops and guerrillas left at least 50 people dead.

Clashes between the army and the rebel Revolutionary Armed Forces of Colombia (FARC) continued tonight near the town of Guayabetal, 30 miles southeast of Bogota. The rebels tried to seize the town Saturday but were repelled by 1,000 troops backed by aircraft. Today, the town was squarely in government hands, the army's press office said. "This terrorist attempt failed miserably," said armed services chief Gen. Fernando Tapias.

A Colombian television reporter who has been covering the fighting, Astrid Legarda of RCN, was wounded in the abdomen when a man who was guiding her mishandled a grenade and it exploded in his hands. The man was killed.

In Saturday's fighting, Guayabetal residents ran for cover and motorists hid beneath vehicles while army Black Hawk helicopters pounded the mountainous region with rockets and machine-gun fire. Tapias said 44 rebels died in the fighting, although as of this afternoon reporters had been shown only 20 bodies. Five soldiers and a policeman also were reported killed.

The FARC, which has about 15,000 combatants, is one of two main guerrilla groups that have been fighting the Colombian government for more than 35 years. At least 30,000 people have died in the civil war. The latest clashes occurred as Secretary of State Madeleine K. Albright visited the Colombian city of Cartagena to promote a proposed $1.6 billion aid package to help the government fight drug trafficking.