CANBERRA : Two American fighter jets dropped four unarmed bombs into Australia’s Great Barrier Reef Marine Park when a training exercise went wrong, said the US Navy.

The two AV-8B Harrier jets launched from aircraft carrier USS Bonhomme Richard each jettisoned an inert practice bomb and an unarmed laser-guided explosive bomb into the World Heritage-listed marine park off the coast of Australia’s Queensland state on Tuesday, said the US 7th Fleet in a statement on Saturday.

The four bombs, weighing a total 1.8 metric tons, were dropped into more than 50 metre of water, away from the coral formations, to minimise possible damage to the reef, said the statement. None exploded.

The jets from the 31st Marine Expeditionary Unit had intended to drop the ordnances on the Townshend Island bombing range, but aborted the mission when controllers reported the area was not clear of hazards. The pilots conducted the emergency jettison because they were low on fuel and could not land with their bomb load, said the Navy.

The emergency happened on the second day of a biennial joint training exercise that brings together 28,000 US and Australian military personnel for three weeks.

Australian Senator Larissa Waters, the influential Greens party’s spokesperson, called the dumping “outrageous” and said it shouldn’t be allowed.