Colombian President Juan Manuel Santos (C) in Cali on April 15, 2015
Bogota (AFP) - Colombian President Juan Manuel Santos lifted a suspension of air strikes against the FARC after the Marxist guerrillas were suspected in the killing of 10 soldiers in a pre-dawn attack.
The attack in western Colombia, which also left 20 soldiers wounded, was the deadliest since the start of peace talks more than two years ago, officials said.
"I have ordered the armed forces to end the order suspending bombing raids against FARC camps until further notice," said Santos.
"Let this be clear to the FARC: I'm not going to be pressured... by vile acts like this to make a decision on a bilateral ceasefire."
Late last year the FARC declared a unilateral ceasefire in a bid to advance peace talks that have been under way in Havana since November 2012.
Santos has refused to commit to a bilateral ceasefire until there is a comprehensive peace agreement, but had suspended air raids in recognition of the move.
Wednesday's attack occurred in a remote mountainous area in Cauca province, a stronghold of the Revolutionary Armed Forces of Colombia (FARC), who have been battling the Bogota government for five decades.
A senior military official said the infantry troops were ambushed as they conducted a patrol.
"They were attacked with explosives, grenades and firearms," General Mario Augusto Valencia, the commander of the army's Third Division, told reporters.
Cauca governor Temistocles Ortega earlier told Blu radio the soldiers came under fire in a hamlet known as La Esperanza.
The wounded were evacuated with the help of the Red Cross and emergency personnel, but bad weather and the remote location were hampering the operation, Valencia said.
- Impact on peace process -
The attack underscored the difficulty of putting an end to the conflict, now over a half century old and easily Latin America's longest.
"We deplore the deaths of the soldiers in Cauca. This is precisely the war that we are trying to end," Santos said on Twitter.
In Havana, a FARC spokesman expressed regret over the bloodletting, but blamed the government's "incoherence in ordering military operations against a guerrilla force observing a truce."
"Whether it was an ambush or a counter-ambush, what we have before us is some dead Colombians," said the spokesman, Pastor Alape, calling on the government to join the FARC in a ceasefire.
Jorge Restrepo, the head of a research center that specializes on the Colombian conflict, said the attack was a "serious" blow but would not lead to a breakdown in the peace talks.
He added that it might even serve "to accelerate the negotiation of a definitive ceasefire in Havana."
The public defender for human rights, Jorge Armando Otalora, denounced the guerrillas' "rupture of the unilateral ceasefire," calling it "an open contradiction with the discourse of the FARC negotiators in Havana."
The attack also aroused opponents of the peace talks, led by former president Alvaro Uribe, a popular figure in Colombia for his hardline campaign against the FARC from 2002 to 2010.
"Santos' peace is the extermination of the armed forces," Uribe stormed on Twitter.
"Santos, please don't deceive us any more, don't justify the assassination of our soldiers with the story about 'the war that wants to end.'"
Formed in 1964 amid a peasant uprising, the FARC has an estimated 8,000 fighters, deployed in rural areas of the country.
More than 200,000 people have died and another five million have been uprooted as a result of the conflict.