The recent violence "provided a clear indication that there has been an erosion in the gains made in strengthening reconciliation, social cohesion and peacebuilding in post-war Sierra Leone", said Chernor Maju Bah, the leader of the All People's Congress (APC) party.
He also demanded records of all those incarcerated and killed during and after the protests, and urged authorities to release the bodies of the dead for "dignified burial rites".
On Friday, President Julius Maada Bio -- who had cut short a vacation to the United Kingdom -- blamed the demonstrations on opposition parties, claiming that his political rivals had attempted to overthrow his government in a "premeditated" insurrection.
Bio, a general turned politician who was elected in 2018, specifically pinpointed the APC, his party's main political rival and the country's former ruling party, as well as People's Power In Politics (PPP), a pressure group.
On August 10, a protest about the cost of living spiraled into deadly clashes between security forces and young men demanding the president resign.
Violence erupted in several parts of the West African country, with the authorities imposing an internet blackout in response.
The police described the incident, which left at least four officers and several protesters dead, as an "insurrection by misguided individuals".
It said earlier this week it had been conducting raids on "hideouts for perpetrators".
During one of those raids on Sunday in the city of Makeni, Hassan Dumbuya, alias Evangelist Samson -- a social media influencer and APC member -- was killed in crossfire, the statement said.
It said former combatants had fired on police during a street chase and a light submachine gun was found at the scene.
Police also said they had made multiple arrests in Makeni and the capital Freetown.
The interior ministry said at least 38 minors had been arrested across the country and were being held in detention.
Sierra Leone has had a reputation for relative stability since the end of a civil war that ran from 1991 to 2002 and left about 120,000 dead.
But the economy, heavily dependent on minerals, has struggled to rebound, and the country's eight million residents live in one of the poorest nations in the world.