WASHINGTON (AFP) - A white police officer has been indicted on a felony assault charge in the northeastern state of Delaware after being caught on video kicking a black man in the face, US prosecutors said Friday.

Police officer Thomas Webster was indicted Monday after the case, which dates to an incident on Aug 24, 2013, was presented before a second grand jury.

The indictment alleged that Webster "did recklessly cause serious physical injury to Lateef Dickerson, by kicking him."

A video taken by a camera mounted in a patrol car showed Webster kicking Dickerson while shouting "go on the f***ing ground."

Dickerson, who suffered a broken jaw, was seen lying on the ground unconscious.

The incident occurred after police intervened in a fight outside a petrol station in Dover, Delaware.

Webster, who was suspended, was cleared by a first grand jury that heard evidence in the case.

But Delaware's new Attorney-General Matt Denn "reviewed the evidence in the case, and as a result of that review, asked prosecutors to re-present the case to a grand jury," his spokesman Carl Kanefsky told AFP.

"He was indicted on second degree felony assault and released on bond."

Racial tensions have flared across the United States since last summer when the shooting death of an unarmed black teenager in Ferguson, Missouri set off weeks of sometimes violent protests.

In the most recent high-profile racial unrest, riots erupted in Baltimore late last month after the death of a 25-year-old black man, Freddie Gray, from injuries suffered in police custody.

Six police officers were charged over his death, and the US Justice Department has launched a federal probe into police practices in Baltimore.