Armed fighters have released at least 900 prisoners in Beni, eastern Democratic Republic of Congo, the local mayor Modeste Bakwanamaha, announced.
Only about 100 remained following the simultaneous assault on the Kangbayi central prison and on the military camp that provides security to it.
Mr Bakwanamaha believes that a group known as the Allied Democratic Forces (ADF) carried out the attack.
Among the inmates who have escaped from Kangbayi central prison are convicted militia members.
ADF have been active in east DRC since the 1990s and have killed more than 1,000 civilians since the start of 2019, according to UN figures, despite repeated military campaigns aimed at destroying it.
About six years ago, ADF started to attack villages, killing people using machetes and guns. They have also abducted hundreds over the years.