AUSTRALIA: New South Wales Police say several people of Middle Eastern appearance have been attacked by a mob at Sydney's Cronulla Beach.

Thousands of people have gathered at the beach in response to calls to retaliate for the bashing of two lifeguards a week ago.

Assistant Commissioner Mark Goodwin says several people have been the victims of racial attacks.

"In terms of crowd swells against some people of Arabic extraction ... some of those people that have been targeted have been Australian-born people that attend this beach in a quiet and relaxing manner," he said.

Six people have been taken into custody and four have been charged.

Assistant Commissioner Goodwin says police are in control of the situation.

"I'm satisfied that we have the police resources that we require and that they are being tactically deployed at my direction," he said.

Ambulance attacked

The Ambulance Service of NSW says one of its vehicles has been attacked.

One ambulance officer has been hit over the head with a glass bottle and another on board has received lacerations.

The ambulance had been transporting six injured people.

Of those, one has been taken to hospital in a serious but stable condition and the rest are being treated for minor injuries in a secure location away from the crowds.

Police say two bottle shops have been closed and a nearby club has agreed not to let any more people in.

Earlier in the day the atmosphere had been party-like despite the large crowd, which some estimates say numbers 5,000 people.

That changed when a man of Middle Eastern appearance was chased into a hotel bistro.

Within a minute the hotel was surrounded by several thousand people screaming and chanting.

About a half an hour later a fight broke out across the road and police led away a man with a shirt over his head as the crowd lobbed beer cans at him.