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.

Police spokesman Sgt Barry Montgomery told the LA Times that officers had been responding to reports of a robbery in the area.

He declined to say how many officers were involved in the incident but confirmed that none had been injured. He did not identify the dead man.

The BBC's Alastair Leithead in LA says it is unclear from the video what exactly happened, but police would be allowed to use deadly force if the man had a weapon.

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

The shooting dead of Michael Brown - an unarmed black 18-year-old - by a police officer in Ferguson, Missouri, last August sparked protests across the US.

Tensions were further inflamed in January when police in New Jersey were caught on camera shooting dead a black man as he stepped out of a car with his hands raised.