Antony Mwalushayi, a spokesperson for the army's operations against armed groups in North Kivu province confirmed that five police officers had been killed and three police jeeps burned in the unrest. He did not say how the officers were killed.
Protests broke out in western parts of Butembo Friday, with participants angry about how the prison in the middle of the city was attacked on Wednesday with such apparent ease, said Van Germain Katsiwa, a representative of a local civil society group.
"The situation is critical - we've seen a massive break-out in Butembo" he said by phone.
Congolese troops have been able to quell the unrest but the mood in the city remained tense,
The army has blamed the jailbreak on the Allied Democratic Forces (ADF), an Islamic State-linked militant group from Uganda that has been active in eastern DRC since the 1990s.
However, Islamic State claimed responsibility for the attack on Thursday, according to the U.S.-based SITE Intelligence Group, which follows militant websites.
Escapes are common from DRC's overcrowded and poorly secured prisons. In 2020, the ADF was linked to a prison break that freed more than 1,300 inmates in the city of Beni, which is also in North Kivu province.