Bogota, Colombia ? Guerrillas attacked an army base, ambushed police and launched other attacks Saturday across Colombia, killing 10 people, as Colombians voted in a referendum seen as a test of President Alvaro Uribe’s support.

Rebels of the Revolutionary Armed Forces of Colombia attacked a base of the army’s Sixth Brigade early Saturday in the western city of Ibague with explosives and gunfire, killing one soldier and wounding two.

FARC rebels also ambushed police patrols near the southwestern villages of Jambalo and Silvia, killing six officers.

A bomb planted by suspected rebels exploded outside a milk processing factory in the northwestern town of Yarumal, killing three people and wounding five. The manager of the Colanta factory is Jenaro Perez, a friend and political ally of Colombia’s president.

FARC rebels also blocked a major highway leading from the third-largest city, Cali, to Buenaventura on the Pacific coast, and burned a half-dozen trucks.

A Colombian senator narrowly escaped that attack. Upon seeing the rebel roadblock, Sen. Juan Carlos Martinez’s driver pulled a U-turn. The car came under a hail of rebel gunfire but no one aboard was hurt.

The attacks were the rebels’ response to government attempts not only to strengthen its hand through the referendum on Saturday but also to stage municipal and state elections today through the country.

The U.S. Embassy in Bogota warned Americans that terrorist attacks “could specifically target popular commercial and nightlife centers, including shopping complexes, restaurants and populated areas with concentrations of such establishments.”

Gen. Jorge Enrique Mora, the commander of Colombia’s armed forces, discounted the effects of the rebel attacks.

“These threats will not interfere with Colombia’s democratic fiesta,” Mora told RCN radio.

Even before the election-day violence, there were indications that voter apathy could undermine the referendum. To be valid, at least 25 percent of registered voters, or 6.2 million people, needed to participate. A recent Gallup poll found that only 23 percent of voters would do so.

Uribe urged voters to turn out as their patriotic duty.

“The referendum is not a miracle but it is a step against corruption and political misconduct,” Uribe said before voting in Bogota’s main Plaza Bolivar. “It is a step toward strengthening public order.”