The 19-year-old man had been with friends who were walking along the bike track near the local Surf Life Saving Club around 8.05pm Saturday, when he collided with a cyclist of a similar age, authorities said.

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"This guy was riding a skateboard whilst talking to his friends and another male has come around a corner on a push bike and hit him, and knocked him unconscious," said NSW Ambulance Duty Operations Manager Illawarra Norm Rees.

The skateboarder suffered head injuries and lost consciousness, and was subsequently found to have "a small cerebral bleed" (bleeding on the brain).

He was flown to St George Hospital by rescue helicopter, which landed at Thomas Dalton Park.

The bike rider suffered fractured ribs and bumps to his head. He was taken to Wollongong Hospital by road ambulance in a stable condition.

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