FREMANTLE defender Michael Johnson is being investigated by police over an alleged assault in Perth in the early hours of Sunday morning.

The West Australian reported a Bunbury man had alleged to police he was struck by a 32-year-old man after a confrontation in a takeaway food shop.

The man filmed a video of the lead-up to the incident, which was shown on Channel Seven's Perth news on Monday night.

The video shows a man alleged to be Johnson with his pants down in a kebab shop moments before the alleged assault.

Fremantle released a statement on Tuesday from CEO Steve Rosich.

"We are treating the matter seriously and we are very disappointed that Michael placed himself in such a situation last weekend," he said.

"Michael, who was on leave at the time, is a senior player and a member of our leadership group.

"In this instance the position Michael placed himself in, including his alleged behaviour, was not acceptable. As a club we support the person and challenge the behaviour.

"Thankfully, there was not anyone seriously injured.

"The club has advised the AFL and will continue to update the AFL until the matter is resolved.

"Given that the matter is still being investigated by police, the club is not in a position to comment further or discuss any possible sanction until the investigative and legal process is completed."

Johnson, 32, played only four games in 2016 because of a hamstring injury.

The veteran defender was welcomed back into Fremantle's leadership group in January, having been dropped from it in 2010 after he was charged with drug possession.