Disturbing video has emerged of a man appearing to rob a door-to-door salesman in south Auckland.

A video showing an apparent robbery of a door-to-door salesman in south Auckland has been posted online, prompting a police investigation.

The video is filmed by a man who appears to be in a garage where a salesman is trying to sell him mobile phones.

The man says to the salesman: "Empty your pockets bro".

SUPPLIED/YOUTUBE The man (pictured) has filmed himself appearing to rob a salesman trying to sell mobile phones.

Initially the salesman ignores him but the man persists, asking "does it look like I'm playing bro? Bro does it look like I'm f***ing playing bro?"

The salesman says he has nothing but then hands over two mobile phones.

A police spokeswoman said the incident was being investigated.

The video was believed to have been uploaded to Facebook earlier this week.

It was shared on YouTube on Wednesday by a man who described the alleged thief as a "wannabe gangster on government benefits".

It was believed to have been filmed in Manurewa, south Auckland, 3 News reported.