Police in the US city of Cleveland have reportedly used pepper spray on Black Lives Matter protesters.
Police on Sunday also arrested several activists who came from across the United States to attend the national convention of the Movement for Black Lives in Cleveland, Ohio.
Hundreds of activists gathered at Cleveland State University for the conference to discuss rising tensions between police and the black people.
Following the closing session of the conference on Sunday, dozens of people held a demonstration against the police brutality.
Police accused the protesters of blocking traffic and attacked them with pepper spray, reports said.
Videos posted online show a police officer spraying pepper powder virtually at a camera operator.
According to eyewitnesses, protesters were pepper-sprayed repeatedly by police.
The killings of several unarmed black men by white police officers in recent months, and decisions by grand juries not to indict the officers, have sparked a national debate on race and led to mass street protests all over the United States.
Large-scale demonstrations were held across the US after a series of high-profile incidents of white police officers killing unarmed African-American men, including Michael Brown in Ferguson, Missouri; Tamir Rice in Cleveland, Ohio; Eric Garner in Staten Island, New York and Walter Scott in North Charleston, South Carolina.
The recent unrest in Baltimore over the death of Gray was the most violent in the United States since the protests in Ferguson following the fatal shooting of 18-year-old Brown by a white police officer.