A video has captured the moment US police shot and killed a homeless man after an altercation in downtown Los Angeles.

The graphic film shows a violent struggle between the man and several officers in the city's Skid Row area.

As the police try to subdue him, a voice is heard shouting "Drop the gun!". Seconds later, five gunshots ring out.

Police are yet to confirm whether the man was armed.

The incident took place in Los Angeles's notorious Skid Row district, which has a large homeless population.

The exact circumstances of the shooting are not yet known but one report said the police had been called out to investigate a suspected robbery.

Last year, highly publicised killings of black men sparked weeks of protests in the US.