Footage has emerged appearing to show the moment a masked gunman began shooting at police in Baton Rouge, Louisiana, killing at least three officers.

In the video shots are heard ringing out and a large police presence can be seen. Officers were called to reports of a suspicious person.

It was at that stage unclear how many shooters were involved, thought police later said they had shot dead the only suspect.

Kip Holden, Mayor-president of the East Baton Rouge Parish, told CNN: "There is still an active scene. They are investigating.

"Right now we are trying to get our arms around everything. It's just been one thing after another."

Baton Rouge's chief administrative office confirmed to a local newspaper The Advocate that at least two officers had died with another also "feared dead".

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It comes just a week after protests over police brutality following the death of a 37-year-old black man, Alton Sterling, who was shot dead by officers at close range.

A video of the incident filmed on a mobile phone purported to show two white officers holding the father-of-five down before shooting him. A second video appears to show them pulling a gun out of his back pocket after he was on the ground.

Mr Sterling's death - and that of two other black men in as many days in Falcon Heights, Missouri and Brooklyn, New York - brought a wave of protests by the Black Lives Matter movement across the US.

At a demonstration in Dallas five people officers were killed by a sniper who was unconnected to the movement. Micah Xavier Johnson said he wanted to "kill white people" before being killed by a police robot.

The motive for the Baton Rouge shooting is currently unclear.