Image copyright AFP Image caption James Packer is one of Australia's wealthiest men

Police have launched an investigation into a street brawl between an Australian billionaire and a TV network head that led to a media frenzy.

Gambling tycoon James Packer and David Gyngell, who heads the Nine Entertainment Group, were seen fighting at Bondi Beach on Sunday.

It is not clear what caused the brawl between the two, who are good friends.

The incident has dominated the Australian media, with photos reportedly sold for a six-figure sum.

"Eastern Suburbs Local Area Command has commenced an investigation into an incident that occurred about 14:00 Sunday... at Bondi Beach," a police statement said.

"Police have not yet received an official complaint but have appealed to anyone who witnessed, or has vision or images of the incident."

James Packer, son of media tycoon Kerry Packer, is one of Australia's richest men, with an estimated wealth of around A$6bn ($5.6bn, £3.3bn) from his gaming empire.

David Gyngell, a top-level media executive, was best man at his wedding, as Mr Packer was at his.

Photographs showed the two men trading punches, wrestling and swapping headlocks. Video footage then showed them grappling on the ground, with three other men trying to separate them.

After the fight, the men released a joint statement.

"We have been friends for 35 years and still are," it read. "In that time we have had our fair share of ups and downs. We respect each other and neither of us will be commenting further."

The brawl has attracted enormous media interest in Australia, with tabloids devoting pages of coverage to what one is calling the "Bondi biffo".