President Alvaro Uribe (search) flew to southwest Colombia to oversee a counterattack against leftist rebels on Sunday, a day after 25 soldiers were killed in attacks across the country that shattered hopes that the insurgents were nearing defeat.

More than 1,000 troops backed by helicopter gunships hunted down several hundred rebels believed to be heading for the nearby Ecuador (search) border to seek refuge, the army said.

"The murder of our soldiers pains us greatly," Uribe said after meeting with military commanders in Puerto Asis, some 330 miles southwest of Bogota (search).

"But to make concessions to terrorism or to bow to terrorism undermines democracy," he said. Uribe added that he intends to discuss the situation along the border with Ecuadorean authorities.

As many as 300 members of the Revolutionary Armed Forces of Colombia, or FARC (search), on Saturday attacked oil wells near Puerto Asis and ambushed an army convoy, killing at least 19 soldiers. Rebel casualty figures were not known.

Another 19 soldiers who went missing during the combat were found alive and well early Sunday, said Acting Army chief Gen. Hernan Alonso Ortiz. The soldiers got separated from their unit during the clashes and had been unable to contact their commanders.

A further six soldiers died Saturday when they fought rebels blockading a road in northeast Colombia — making it the deadliest day for the military since Uribe came to power three years ago on pledges of crushing the 40-year-old insurgency.

The FARC has this year launched some of its boldest attacks on the military since peace talks collapsed in February 2002, killing more than 130 soldiers.

The rebel offensive came after military commanders claimed that a U.S.-backed, 3-year-old military buildup had forced the FARC into irreversible decline.

Analysts say the FARC wants to undermine Uribe's re-election hopes by showing that his security crackdown has failed and that only peace talks with a leader more sympathetic to the rebels can lead to peace.

Army officials maintain the FARC is made up of 12,000 fighters now, down from 18,000 a year ago, due to deaths, captures and desertions brought on by the government offensive.

Colombia's drug-fueled conflict pits the FARC and the smaller National Liberation Army against a handful of right-wing paramilitary militias and government forces, killing more than 3,000 people every year.