Fighters from Colombia's main leftist rebel movement staged an attack from Venezuelan territory Monday on an army patrol that was guarding a telecommunications tower, killing at least 12 soldiers and wounding four others, Colombian officials said.
Venezuelan President Hugo Chavez responded quickly, saying he had sent additional troops to the region where the attack occurred to ensure no rebels passed into his country's territory.
"We are not going to permit irregular groups of whatever stripe to use Venezuela as a place to camp, train or attack forces of other countries, in this case Colombia," Chavez said in a phone call to Venezuelan state TV.
He said he had spoken about the attack with Colombian President Juan Manuel Santos, who later said in a brief televised appearance that Chavez told him he had sent two army brigades to the border.
"The brigades have clear instructions to try to find these FARC bandits. And if they do they are going to capture them, and if they resist they will use their weapons," Santos said. "Those are the instructions that President Chavez gave, to fire on them."
Relations between the two countries have improved significantly since Santos' mid-2010 election.
The Revolutionary Armed Forces of Colombia, or FARC, has long used Venezuela as a sanctuary for its guerrillas. FARC leaders have also taken refuge there. Venezuela has become less hospitable to the rebels since Santos took office but has not yet turned over a FARC commander, Julian Conrado, it arrested a year ago who is wanted by Colombia's government for homicide, kidnapping and rebellion.
The commander of the Colombian army's 1st Division, Gen. Jorge Eliecer Suarez, told The Associated Press that FARC rebels attacked his troops Monday from Venezuelan territory then withdrew back into the neighboring country.
He said that a group of 60 to 80 rebels attacked and that the firefight lasted about an hour.
La Guajira province Gov. Juan Francisco Gomez said 12 soldiers, including a second lieutenant, were killed. He said the wounded were taken to a hospital in the regional capital of Maicao.
The death toll was among the highest in a single FARC attack this year on the Colombian military.
Analyst Ariel Avila of the Nuevo Arco Iris foundation in Bogota said there had been about 550 FARC attacks in the first four months of this year, an increase of about 3 percent from a year earlier and 15 percent from four years ago.
He said the FARC is interested in regaining territory lost in the 1990s in the La Guajira region, where the rebels extort ranchers and miners.
Some conservatives, including the previous president, Alvaro Uribe, contend that Santos has lost momentum against the FARC after a decade of weakening the rebels, in particular by hunting down and killing their top leaders.
Associated Press writer Fabiola Sanchez in Caracas, Venezuela, contributed to this report.