Washington, D.C. police said late Sunday 33 people had been arrested between Saturday and Sunday after protests in the District led to unrest and violence.
Eight police officers were also injured during the demonstrations, officials said.
Earlier rallies of mostly unmasked loyalists of President Donald Trump were intended as a show of force before the Electoral College met to formally elect Democrat Joe Biden as the 46th president. Trump, whose term will end Jan. 20, refuses to concede, while clinging to claims of fraud that have been rejected by state and federal courts, and Friday by the Supreme Court.
On Sunday, police said four people were stabbed near the Black Lives Matter Plaza, while 33 unrelated arrests were made during the violent clash between outgoing president Trump's supporters, anti-Trump protesters and the authorities.
The police said stabbing victims suffered non-life threatening injuries but they were hospitalized for monitoring and treatment.
At least nine people who had to be transported to nearby hospitals following the arrest of Phillip Johnson for assault with a deadly weapon. Johnson's arrest took place after an argument that resulted in stabbings.
Eight police officers were injured and a Black Lives Matters sign was burned in a nearby street. Some other signs under the BLM movement were either taken down or destroyed.
In some videos circulating online, a single gunshot can be heard. Police confirmed one person was shot. Another video shows a man running while carrying a gun.
Many members of far-right group Proud Boys attended the Saturday rally. "Four more years!" were among the popular chants that were used by Trump's supporters.
Police also detained some Proud Boys during the rally after they attacked anti-Trump protesters in the capital. Other protests occurred in Minnesota and Georgia.
Trump's supporters called for the election results to be overturned, promising they won't recognize president-elect Joe Biden.
Trump has entered a sixth week of his refusal to concede despite 50 states confirming the results of the 2020 presidential election. On Monday, the Electoral College will cast its votes.
Analysts said Trump's claims of alleged cheating during elections encouraged his supporters to continue protesting.
Trump has been active on Twitter, posting a video of Saturday's rally. On Sunday he called the 2020 election the "MOST CORRUPT ELECTION IN U.S. HISTORY."
