BOGOTA, Colombia — The top peace negotiator for the Revolutionary Armed Forces of Colombia announced Thursday that he and a small cadre of hardline supporters are taking up arms again, accusing President Ivan Duque of failing to uphold the 2016 accord that sought to end a half-century of bloody fighting.

In a video published before dawn, Luciano Marin appeared alongside some 20 heavily armed guerrillas dressed in camouflage fatigues condemning the conservative Duque for standing by idly as hundreds of leftist activists and more than 150 rebels have been killed since demobilizing as part of the peace deal.

“When we signed the accord in Havana, we did so with the conviction that it was possible to change the life of the most humble and dispossessed,” said Marin, better known by his alias Ivan Marquez, in the more than 30-minute video. “But the state hasn’t fulfilled its most important obligation, which is to guarantee the life of its citizens and especially avoid assassinations for political reasons.”

In the video, Marin, speaking from what he said were Colombia’s eastern jungles in the Amazon rainforest, stood alongside several former FARC leaders, including ideologue Seuxis Hernandez, alias Jesús Santrich, who abandoned the peace process after the US ordered his arrest on drug charges.

A commander from the National Liberation Army, or ELN, a more radical guerrilla army that has filled the void left by withdrawing FARC rebels in far-flung rural areas, welcomed the pronouncement, which came as a shock to many Colombians.

“Better late than never,” said the fighter who goes by the alias Uriel. The commander of ELN troops in Colombia’s western jungles, he released a video on social media in which he appeared along a river with his face masked and fist clenched in the air.

But Rodrigo Londono, who had been the FARC’s top military commander and now heads its legal political party, distanced himself from his former comrades, with whom relations have been strained in the past year. In an interview with Blu Radio, he apologized to his fellow Colombians and the international community, saying the vast majority of rebels remain committed to the peace process despite rising security risks.

“I have mixed feelings,” said Londono, who is better known by his alias Timochenko. “It’s an unfortunate development, but at the same time, it leaves things clearer and ends the ambiguity because we had been facing a complex situation for some time.”

There was no immediate reaction from Duque. But his peace commissioner, Miguel Ceballos, called for the special peace tribunals investigating the rebels’ war crimes to strip the deserters of benefits under the accord. He also said the government would insist on the rebel leaders’ arrest.

Some 7,000 rebels handed over their weapons to observers from the United Nations as part of the deal negotiated with the support of the US, Cuba and Norway. But smaller rebel groups and drug trafficking gangs have filled the void left by the withdrawing FARC rebels, leaving many Colombians frustrated with the slow pace of implementing the accord.

Duque rose to power last year on a law-and-order platform opposing many aspects of the peace deal, especially provisions that spare rebel leaders jail time in exchange for confessing their involvement in war crimes like the extortive kidnappings of civilians and recruitment of child soldiers.

In office, he’s moderated his views and started implementing ambitious aspects of the accord to build roads, schools and other infrastructure in traditionally neglected areas of the country where the state’s presence has historically been limited.

But critics, including the architects of the peace deal, have accused him of not doing enough to protect leftist activists and aligning with the US to gut the special peace tribunals whose goal is to foster reconciliation and truth-telling for victims instead of seek full punishment for war atrocities.

“90 percent of the FARC remain in the peace process. We must continue to fulfill our obligations to them and repress the deserters with complete force,” former President Juan Manuel Santos, who was awarded the Nobel Peace Prize for his efforts to end the nation’s armed conflict, said in a message on Twitter. “The battle for peace must not stop!”