* Guerrillas show they still have offensive capacity
* More shows of force expected before May election (Adds context, color, paragraphs 8-9)
By Hugh Bronstein
BOGOTA, Nov 10 (Reuters) - Nine Colombian soldiers were killed when their post was attacked by Marxist FARC guerrillas in a southwestern part of the country used as a cocaine smuggling corridor by the rebels, officials said on Tuesday.
The attack by about 200 grenade-throwing guerrillas showed that the Revolutionary Armed Forces of Colombia (FARC) can still mount offensive operations despite President Alvaro Uribe’s U.S.-backed military campaign to crush the 45-year-old insurgency.
The battle took place in the town of Corinto, located in the mountainous province of Cauca. Most inhabitants of the town are members of indigenous groups hard hit by Colombia’s war.
Estimates of guerrilla deaths varied from 10 to 30, but none had been confirmed by the defense ministry.
The battle started late on Monday and continued into Tuesday, according to local officials.
"Nine soldiers are dead and three injured. Combat continues," Cauca Governor Guillermo Gonzalez said.
Uribe called the nine deaths a tragedy. Television images of terrified townspeople, their houses pocked by bullet holes, brought back memories of the 1980s and 1990s when battles like this were common in Colombia.
"I fired three or four magazines and had to retreat," a Colombian soldier told local television. "I saw that my friends were dying. Most of them had been hit by home-made grenades."
Most cities have become safer since Uribe first took office in 2002. But the rebels have dug in throughout the countryside and remain well-financed by the cocaine trade.
Cocaine is produced in Colombia’s southern jungles and transported through Cauca to the Pacific coast for shipment by sea to the United States.
Uribe, whose father was killed in a botched FARC kidnapping in 1983, is a hero to many for his tough anti-FARC stance. He may run for a third term if his backers succeed in amending the constitution to allow him to stand in the May election.
The law already was changed once to allow Uribe to win a second term in 2006. The rebels traditionally step up attacks ahead of elections.
"There has been a reactivation of the FARC in recent months in places like Cauca and Norte de Santander, near the Venezuelan border," said Mauricio Romero, a political science professor at Bogota’s Javeriana University.
"The FARC no longer presents a strategic threat to the state, but they are making the point that they can still do damage despite Uribe’s counteroffensive," Romero said.
(Editing by Will Dunham)