Family's desperate message for missing backpacker

The family of a German backpacker last seen in Perth three days ago have issued a desperate message to him.

Andreas Karl Wacker, 28, was last seen filling up his car at a petrol station in Rockingham, just before 7pm on Wednesday.

Earlier that day he was seen at a gym in Cockbun just before 12.30pm, while prior to that he left his belongings at a friend's house in Yangebup.

His family said they knew something was wrong when he didn't respond to birthday messages last week.

Aunt Andra Malburg said Mr Wacker kept in regular contact with his family while overseas.

"Please contact your mum, contact any of us," she said.

"Your mum is going crazy, she hasn't been sleeping. She's worried sick, we're all worried sick."

Relatives believe he is without his phone, wallet and passport.

But he is believed to have his car - a white Nissan Pathfinder, registration 1BSY613 with camping gear stacked on top.

"This is really our only lifeline we have right now, and so far we've done everything we can," Ms Malburg said.

Anybody who sees Mr Wacker is urged to contact police on 131 444.