(Adds details throughout, army comments)

By Patrick Markey

BOGOTA, May 10 (Reuters) - Ten Colombian soldiers died on Thursday when leftist rebels detonated a bomb on a rural road in the second major guerrilla attack in two days, military officials said.

Local army commander Gen. Hernando Perez blamed the Revolutionary Armed Forces of Colombia, the country's largest rebel group known as the FARC, for the attack in Valle del Cauca province, 143 miles (230 km) southwest of Bogota.

"We believe it was activated by remote control," Perez told local radio.

Two officers and eight soldiers were killed and 10 were slightly wounded in the attack against a military convoy, an army spokesman said.

The ambush, one of the worst this year, came a day after nine police officers were killed by a bomb in Santander province while on an operation to eradicate coca leaf used to make cocaine. Authorities say the FARC is also responsible for that attack.

Violence from Colombia's four-decade insurgency has dropped off sharply since President Alvaro Uribe began a U.S.-backed offensive to push the rebels back into the jungles and disarm the illegal paramilitary squadrons who once fought them.

But the FARC, which began as a peasant army in the 1960s, is still a potent force in rural regions. Urban bomb attacks are less common, but the guerrillas often employ explosives and land mines to ambush military patrols in the remote areas.

Authorities say the FARC and a smaller rebel group, the National Liberation Army, are now both engaged in the country's huge cocaine trade. The two guerrilla groups and paramilitary gangs often battle to control coca crops and smuggling routes.

Buenaventura, Colombia's main Pacific port in Valle del Cauca, has been the target of several attacks this year by FARC militants, whom police say are reacting to a crackdown on drug trafficking in the area.

Colombia has received more than $4 billion in mostly military and narcotics aid from Washington since 2000, but more than 600 tonnes of cocaine leave the world's top producer of the white powder each year for U.S. and European streets.

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