Seven people were shot, including one critically, during protests over the killing of a black woman in her flat in Kentucky.
Breonna Taylor was shot eight times by police when they raided her Louisville apartment in connection with a drugs case in March. No drugs were found at her home, a wrongful death lawsuit, which was launched by her family, said.
Since the beginning of the year, three African American people have died during high-profile encounters with the police and the US Justice Department has been asked to investigate systemic police misconduct.
It comes as thousands of protesters took to the streets in a separate demonstration in Minneapolis over the killing of George Floyd after a white police officer knelt on his neck during an arrest.
At the Louisville protests, police said they did not fire any shots at protesters but made some arrests.
They had earlier tweeted that there was a large crowd in the downtown area around Second Street.
Late on Thursday, Louisville Mayor Greg Fischer shared a post on Twitter which he said was written on behalf of Ms Taylor’s mother, urging protesters to be peaceful.
“Understandably, emotions are high,” he said.
Metro Police spokesman Lamont Washington said the situation in the region “remains fluid and continues to evolve".
The first high-profile black killing took place on February 23 when a former police officer and his son chased down Ahmaud Arbery, 25, when he was out jogging in Georgia.
The ex-officer told police he thought Mr Arbery look liked a person who was wanted in connection with a number of recent break-ins in the area.
After he was chased him, Mr Abery attempted to fight off the son, who had a shotgun, and two bullets were fired, according to a Glynn County Police report.
The Democratic-controlled US House Judiciary Committee asked the Justice Department to investigate the three incidents on Thursday.
The killings of Mr Floyd, Ms Taylor, and Mr Arbery raised questions as to whether police were engaged in a “pattern or practice of unconstitutional conduct,” House Judiciary Chairman Jerrold Nadler and the other Democratic members told Attorney General William Barr in a letter.
“Public trust in the blind administration of justice is being seriously tested by recent high-profile killings of African-Americans,” Mr Nadler wrote.
The three deaths have garnered national attention with civil rights campaigners saying the incidents are the latest in a long history of racially motivated attacks against unarmed black men and women by white police or perpetrators.
The death of Mr Floyd, 46, sparked sometimes violent protests this week, after a video showing him gasping for air while a policeman kneeled on his neck went viral.
It echoed the 2014 death of Eric Garner in New York, which helped fuel the rise of the Black Lives Matter movement.
