The incident happened at the largest prison in the country, located in the capital, Kinshasa.
Reports indicate that the incident happened overnight on September 1.
Residents said gunfire erupted around 1 a.m. and continued until 5 a.m. local time.
"The shooting started at 1 am and continued until 5 am. Between 3 and 5 am they were killing each other, and you could hear grenades going off," a witness who lives close to the prison said.
Although details on the number of casualties and possible escapees remain unclear, government spokesperson, Patrick Muyaya has assured the situation is under control. Police have since cordoned off streets close to the facility.
Makala prison, designed to hold 1,500 inmates, currently houses between 14,000 and 15,000 prisoners. The Justice Minister, Constant Mutamba, announced that the transfer of prisoners to the facility has been suspended while investigations continue.