Bogota, Colombia (CNN) -- Ten Colombian soldiers were killed in a rebel attack Monday, the country's defense ministry said.
The attack occurred in La Guajira province, near Colombia's border with Venezuela.
Two other soldiers were killed in another attack, the ministry said, blaming guerrillas from the leftist Revolutionary Armed Forces of Colombia for the violence.
After the clashes were reported, Venezuelan President Hugo Chavez denied accusations that his country provided safe harbor to FARC guerrillas.
"If we can be useful for a peace process in Colombia, we are available, but not for war. ... We cannot permit that they use Colombia to attack and train. We cannot allow ourselves to get involved in a conflict that is not ours," Chavez said in a telephone press conference broadcast on state-run VTV.
Journalist Fernando Ramos contributed to this report.