Colombia's peace process has been rocked by the surprise arrest of a former top leader of the disbanded FARC rebel army on charges of trying to smuggle several tons of cocaine into the United States.

The arrest on Monday of Seuxis Hernandez, a blind former peace negotiator best known by his alias Jesus Santrich, played into fears among many Colombians that the former guerrillas haven't cut ties to the country's flourishing criminal underworld.

It also triggered an exchange of angry recriminations between conservative critics of the peace process and supporters of the disbanded Revolutionary Armed Forces of Colombia.

More than 100 former rebels and FARC sympathizers gathered late Monday outside the heavily guarded prosecutors' bunker where the 51-year-old Santrich was being held to demand his release. Waving white flags emblazoned with the red rose symbol of the former rebels' political movement, some shouted "freedom" and denounced what they called an act of judicial sabotage by the government and its U.S. backers.

Riot police flanked by a water cannon watched quietly, while inside Santrich was believed to have initiated a hunger strike to demand his release, according to his lawyer.

President Juan Manuel Santos defended the arrest on a U.S. warrant as necessary to maintain the credibility of the peace accord, which Colombians overwhelmingly consider too generous to rebels responsible for atrocities committed during five decades of bloody, armed conflict.

"My hand won't tremble to authorize the extradition," Santos said in a nationally televised address in which he tried to reassure demobilized fighters that they have nothing to fear as long as they uphold their commitments under the 2016 peace accord. "This is what the Colombian people demand. In this aspect, there can't be any room for tolerance or weakness."

Santrich, who joined the guerrilla movement in his 20s and gradually rose into its central command structure, was one of the first rebel leaders to bet on peace. He went to Norway in 2012 to begin negotiations with Colombia's government and then participated in talks that continued the next four years in Cuba, where he earned a reputation as being a hard-line ideologue.

He was picked up Monday at a Bogota residence on charges filed in a New York federal court alleging he conspired with three others to smuggle several tons of cocaine into the U.S. with a wholesale value of $15 million, or $320 million when broken up and sold on American streets.

According to an Interpol notice, Santrich met with cocaine buyers at his residence on Nov. 2, 2017 — a day after one of his co-conspirators delivered a 5-kilogram sample of the narcotic to them at a hotel lobby in Bogota. During the meeting and subsequent negotiations, he and his co-conspirators allegedly discussed plans for a 10-ton drug shipment to the U.S., boasting they had access to cocaine laboratories and U.S.-registered planes to produce and transport the drugs inside Colombia, the world's largest producer of the illegal narcotic.

Even before details of the arrest were known, FARC leaders condemned it as a set-up that would undermine almost 7,000 demobilized rebel fighters' trust in the peace process.

The arrest comes less than a week before President Donald Trump is set to visit Bogota for conversations with Santos in which U.S. claims that Colombia's longstanding support for the drug war flagged during peace talks is expected to feature prominently.

U.S. authorities have doubted the sincerity of the FARC leadership's commitment to abandoning the drug trade as it enters politics, and last year named 21 suspected drug traffickers wanted for extradition who somehow managed to end up on a list of former fighters and their sympathizers entitled to benefits under the peace treaty.

Under terms of the accord, rebels who lay down their weapons and confess their war crimes to special peace tribunals are to be spared jail time and extradition. But they aren't protected for crimes committed after the December 2016 signing.

"The senior leadership never cut ties to the cocaine production that earned them billions of dollars as an insurgence," said Douglas Farrah, a senior visiting fellow at the National Defense University who has testified to the U.S. Congress on the FARC's criminal ties.

"Like addicts they just can't quit the business," he added.

The FARC long funded their insurgency by leveling a "war tax" on cocaine moving through territory the rebels dominated. Fifty members of its leadership structure — though not Santrich — were indicted in 2006 in the U.S. on charges of running the world's largest drug cartel.