[Warning: Video contains strong language]

Videos uploaded to social media on 12 March purport to show the moments before and after the shooting of two officers during a protest rally outside Ferguson police headquarters in Missouri.

The shooting came just hours after city's police chief resigned in the wake of a scathing US Justice Department report finding his force was rife with racial bias.

Officials have called the attack an ambush following acute tensions between police and minority groups in the St Louis suburb.

Two videos appear to show police and protesters at a rally before the shooting took place.

Another video purports to show the moment after the shooting took place, with people running and taking cover by lying on the ground.

A further video appears to show police officers moving, with a woman heard saying: "That's my son."

A final video appears to show police officers and civilians following the shooting.

Reuters is unable to independently verify the content of the videos, which were obtained from a social media website.

Both officers have been now been released from hospital, a St Louis County Police spokesman said.

St Louis County Police Chief Jon Belmar said a manhunt was underway for a suspect or suspects.

The turmoil in Ferguson was triggered in August by the killing of an unarmed black teenager by a white policeman, thrusting the town into the centre of an intense national debate over the law enforcement's use of deadly force against minorities.