US fighter jets dumped inert and unarmed bombs on the Great Barrier Reef off Australia's coast during a training exercise that went wrong, it has emerged.

The two planes jettisoned four bombs in more than 50m (165 ft) of water, away from coral, to minimise damage to the World Heritage Site, the US navy said.

The jets had intended to drop at a bombing range on a nearby island, but Tuesday's mission was aborted.

Phil Mercer reports.