(Adds mayor's remarks on attack, paragraphs 3-4) BOGOTA, Jan 21 (Reuters) - Six people were killed on Sunday when Colombian rebels set off explosives near a police patrol in the Pacific port city of Buenaventura in the third serious guerrilla attack in a week, authorities said. Two police officers and four civilians died and at least 18 more people were wounded when the two explosives were detonated, a police spokesman said. "The police were drawn in by a fight between two men. As they were approaching, one bomb went off and then a second that ended with this tragic result," Buenaventura Mayor Saulo Quinones told local television. Officials believe the attack could have been retaliation for police counternarcotics operations. Authorities say Buenaventura is an important channel for the Andean country's drug trade involving guerrillas and rival militias. With the help of millions in U.S. aid, President Alvaro Uribe has reduced violence from the 40-year conflict by sending troops to retake areas under rebel control and demobilize illegal, right-wing militias who once fought guerrillas. The Revolutionary Armed Forces of Colombia, or FARC, the country's largest left-wing rebel group, is still strong in rural areas. U.S. and Colombian officials say the FARC is a drug-trafficking terrorist organization. A rebel car bomb destroyed most of a milk storage plant run by Swiss firm Nestle on Wednesday and the FARC days earlier killed five officers with a bomb attack on a police truck near the border with Ecuador. More than 600 troops and police were killed in combat last year and thousands of people are still forced from their homes each year by fighting between state forces and rebels. Colombia is the world's top producer of cocaine, with most of its crop destined for the United States and Europe.
