Suspected Colombian guerrillas kidnapped five oil workers for companies contracted by Occidental Petroleum in the eastern part of the Andean nation, the army and the company said on Saturday, according to Reuters. The latest attack on the oil sector likely by leftist rebels happened in the Arauca province -- one of Colombia's violent border states where the rebel groups vie for control over resources and illegal cross-border activities. "Some people working as contractors for an oil company here in the department of Arauca were traveling, two people carrying handguns in civilian clothes proceeded to threaten them and kidnap them," General Jaime Reyes, commander of the 18th Brigade, said on Caracol radio. "We've started operations in the sector." The commander did not blame the kidnapping -- which happened on Friday night -- on any group, but the smaller ELN rebels have a strong presence in Arauca, and Colombia's largest guerrilla group, the FARC, also operates in the province. A representative of Occidental told Reuters the five were contractors for two companies that worked for Occidental in its Caricare oil field, which produced an average of 12,000 barrels per day last year. Rebels have been fighting the Colombian state since the 1960s, and although security has improved under a U.S.-backed crackdown launched a decade ago, kidnappings and attacks still happen regularly, especially against the oil sector.