The victims were members of the Patriotic Union (UP) communist party that was formed in the 1980s during an attempt by then-president Belisario Betancur to make peace with the Revolutionary Armed Forces of Colombia (FARC).

The Special Jurisdiction for Peace (JEP) found that "of the 5,733 victims, 4,616 were victims of murder" while the rest were "forcibly disappeared," the report said.

"The violence against the UP members was carried out mainly by state agents and paramilitaries on a massive, generalized and systematic scale," added the JEP.

Among those murdered were two presidential candidates for the UP, Jaime Pardo and Bernardo Jaramillo, as well as a handful of active legislators.

The party was reformed in the last decade and currently forms part of the Historic Pact leftist coalition whose presidential candidate Gustavo Petro leads opinion polls ahead of next month's vote.

The JEP has the authority to offer alternatives to jail time to people who confess their crimes and make reparations.

It received witness statements from 150 people linked to the attacks against the UP, the majority of whom were members of the security forces and intelligence agency.

The tribunal has also opened investigations against guerrillas, state agents and paramilitaries into kidnapping, recruitment of minors, political violence and the murder of civilians during the armed conflict that ended in 2016 with the signing of a peace deal that saw FARC lay down its arms and form a political party.

Since 2017, the JEP has charged former FARC commanders with the kidnapping of at least 21,000 people and the recruitment of 18,000 minors.

Dozens of former members of the military have also been charged with the murder of 6,400 civilians who were executed and then passed off as combatants in return for benefits in a scandal known as the "false positives."