BOGOTA, Colombia (AP) _ Leftist guerrillas attacked two towns Saturday, and officials said 21 people were killed in the fighting. They said it was one of the bloodiest rebel offensives in three decades of fighting.

The insurgents belonged to the country's two most active guerrilla groups, the Revolutionary Armed Forces of Colombia and the National Liberation Army, the army said. The two bands have carried out joint attacks against the army and police in recent months.

An army statement said about 1,000 rebels launched dawn attacks on the towns of Taraza and Caceres in northern Colombia. The statement said at least 14 rebels, six soldiers and a police officer were killed. Another 15 were wounded, it said.

In fighting over several hours, the rebels blocked highways leading to the towns to keep the army from sending in reinforcements. The rebels finally retreated with soldiers in pursuit, the army said.

The offensive came days after the two guerrilla groups offered to enter negotiations with the government of President Cesar Gaviria.

Gaviria has said the guerrillas must call a cease-fire first. The rebels maintain both sides should do so.

Another of Colombia's main rebel groups, the National People's Army, has suspended attacks and begun peace talks with the government.

Among those killed in the fighting was the commander of Taraza's army base, Lt. Col. Jaime Fajardo. He was one of the highest ranking army officials killed in 30 years of fighting between the military and the rebels.

Meanwhile, the Colombian government has approved the extradition of a drug suspect to the United States, local newspapers reported Saturday.

A government council headed by Gaviria on Friday ordered the extradition of Jairo Correa Alzate to Jacksonville, Fla., where he is wanted on drug trafficking charges, said Bogota's El Siglo newspaper.

Correa, 32, has less than one week to appeal the decision before being extradited.

The pending extradition would be the first since Oct. 8, when Joaquin Oswaldo Gallo Chamorro was sent to the United States to face cocaine trafficking charges.

The government has extradited more than a dozen drug suspects to the United States since August 1989. The government's war on drugs began following the slaying in that month of Sen. Luis Carlos Galan, an anti-drug crusader, by the Medellin drug cartel.

Gaviria had managed Galan's campaign for the presidency, and later entered the race pledging to uphold the government's strict anti-drug policies.