BEIJING, May 30 (Xinhua) -- The police killing of George Floyd, an unarmed 46-year-old black man, in the city of Minneapolis, Minnesota on Monday evening has sparked waves of outrage across the United States.

For the fourth straight night following the death of Floyd at the hands of a white police officer while in custody, thousands of demonstrators have poured into streets in multiple U.S. cities to denounce the police brutality and racial discrimination.

The latest instance of police violence has once again brought the public attention to the racial divide which has kept tearing the U.S. society apart.

The following is a list of major racial riots between police and African Americans in recent years.

-- On June 19, 2018, Antwon Rose Jr., a 17-year-old African American teenager, was shot three times in the back by an East Pittsburgh police officer in Allegheny County as he fled a car suspected to be involved in an earlier shooting on that day.

Rose's death sparked days of demonstrations in Pittsburgh demanding justice before his funeral, as protesters questioned police officer Michael Rosfeld's use of deadly force.

-- On Sept. 20, 2016, Keith Lamont Scott, a 43-year-old African American, was fatally shot by police in the city of Charlotte in North Carolina, southeastern United States, sparking protests by African Americans against racial discrimination and injustice by police.

-- On Aug. 13, 2016, a confrontation between police and protestors turned violent in Milwaukee in the midwestern U.S. state of Wisconsin, after a police officer killed an armed 23-year-old African American trying to escape from two police officers who had stopped his car.

-- In April 2015, Freddie Gray, a 25-year-old African-American, died in a Baltimore hospital after he was arrested for possessing what the police alleged to be an illegal switchblade.

Gray's death sparked protests and riots in the city in northeastern United States. One year later, U.S. prosecutors dropped all charges against six police officers accused in the arrest and death of Gray.

-- On Aug. 9, 2014, 18-year-old African American Michael Brown was shot dead by a white police officer in Ferguson, Missouri, sparking over two weeks of unrest and clashes between protesters and law enforcement in the town where most of the population are black.

-- On July 17, 2014, a cellphone recorded an unarmed black man, Eric Garner, repeatedly saying "I can't breathe" when a New York officer held him in a chokehold before his death in police custody. Garner's last words were the same ones Floyd spoke as the officer knelt on his neck before he died.

Almost five years later, federal prosecutors said the officer who caused the death of Garner would not face criminal charges.

-- In July 2012, protestors clashed with police over two separate shootings in the city of Anaheim, southern California. Manuel Diaz, 25, and Joel Mathew Acevedo, 21, who were claimed by the police as gang members, were shot dead by police officers.

Protesters set fires, smashed windows and threw rocks at officers. The riots ended with 24 arrests and several injuries.