Colombia's special peace court on Wednesday charged eight former military intelligence officers with war crimes, crimes against humanity and genocide in the deaths of leftist activists decades ago.
Over 5,700 members of a party called the Patriotic Union (UP) were massacred between 1985 and 1993 amid a terror campaign orchestrated by paramilitary groups in collusion with state forces.
Former members of the rebel army FARC founded the party in 1985 after a failed attempt to negotiate peace with the state.
The party's detractors considered it a political arm of the guerrillas at one of the bloodiest moments of Colombia's decades-long conflict.
Opponents secretly monitored UP members before killing or making them disappear without a trace, in a pattern repeated around the country, the court called the Special Jurisdiction for Peace (JEP) found.
A "clandestine criminal apparatus within the strategic intelligence units of the national army... gathered information on previously identified targets," court president Danilo Rojas told a press conference.
"They carried out surveillance, singled out targets and coordinated clandestine operations," Rojas said.
The JEP also charged the individuals with torture and the forced disappearance of out-of-combat guerrillas during the same period, using practices such as violent interrogation to weaken their organizations.
The court came into being after a landmark 2016 peace deal with FARC.
It judges the worst crimes of the conflict, administering alternative sentences to prison for those who tell the truth and provide reparations to their victims.
Right-wing President Abelardo de la Espriella, who came to power in August, strongly opposes the court.
Congress is debating severe budget cuts to it at his request.
