An Ambulance NSW spokeswoman said paramedics were called to a beach opposite Illfracombe Ave in Vincentia at 2.20pm on Thursday after reports a boy had collapsed on the beach and gone into cardiac arrest.

It is understood the boy was running along the beach when he collapsed.

CPR was commenced before ambulance paramedics arrived and took over, the spokeswoman said.

The boy is being flown to Prince of Wales Children’s Hospital at Randwick in a critical condition.