Colombian right-wing paramilitaries have admitted to killing 21,000 people, prosecutors said on Monday.

"We are up to 21,000 murders that have been confessed to," Luis Gonzalez, of the public prosecutor's office, told local radio.

The confessions by the former fighters spanned a three-year period and are part of a peace deal that includes a drive to demobilize 31,000 former fighters, know as the United Colombian Self Defense Forces, or Autodefensas Unidas de Colombia

Gonzalez told radio Caracol that the full extent of the "horrors" may be unknown "because there are still many murders to confess to.

"We have documented around 246,000 cases that occurred in the regions that had the Autodefensa forces," he said.