By Monica Garcia
TAME, Colombia (Reuters) - Nineteen Colombian soldiers were killed in clashes blamed on the country's Marxist FARC guerrillas, defense ministry sources said on Sunday, the heaviest casualties the armed forces have suffered since the government began peace talks late last year.
In the bloodier of the two separate attacks on Saturday, 15 soldiers were killed on a road linking two townships in Arauca province near the Venezuelan border, when they fired explosives at troops protecting an oil pipeline under construction.
The FARC, or Revolutionary Armed Forces of Colombia, have a strong presence in the region and frequently attack the existing Cano Limon-Covenas oil pipeline owned by state-controlled oil company Ecopetrol, which passes through the area.
President Juan Manuel Santos, who traveled to the region on Sunday confirmed the army casualties and said 12 guerrillas were captured during the attack. He ordered extra troops to the region to try to capture the rebels, some of whom had been injured.
"These are the instructions to our forces: don't stop shooting for even a moment until we reach the end of this conflict," Santos said. "All of Colombia must work for peace precisely so that incidents like those that occurred in the last 24 hours never happen again."
Another four soldiers were killed in clashes in Caqueta province in the south of the country in clashes with the FARC, the army said, adding that six guerrillas were also killed.
The FARC is the larger of two left-wing guerrilla movements in Colombia with around 8,000 fighters, the government says, about half the number it had a decade ago. The much smaller ELN, or National Liberation Army, which the FARC has recently strengthened ties, is believed to have around 1,500 guerrillas.
The government began peace talks with FARC leadership in November last year with an agenda that includes disarmament, land reform and the FARC's participation in politics. The talks are taking place in Havana, Cuba.
(Writing by Peter Murphy; editing by Christopher Wilson)