Environmentalists have expressed anger after it emerged that two US fighter jets dropped four unarmed bombs into Australia's Great Barrier Reef Marine Park when a training exercise went wrong.
The two AV-8B Harrier jets launched from the amphibious assault ship 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 Queensland state last Tuesday, the US 7th Fleet said.
The Great Barrier Reef, the world's largest network of coral structures, is rich in marine life and stretches more than 1,800 miles along Australia's north-east coast.
Commander William Marks, spokesman for the US Navy's 7th Fleet, said the emergency jettison was made in consultation with Australian officials.
"There is minimal environmental impact," he told Australian Broadcasting Corporation radio. "It is a safe situation for the environment, for shipping, for navigation."
The four bombs, weighing a total of 2,000lbs, were dropped into more than 50 metres (164ft) of water away from coral to minimise possible damage to the reef, the fleet said. 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 navy said.
"There were civilian boats right below them," Cmdr Marks said.
The pilots conducted the emergency jettison because they were low on fuel and could not land with their bomb load, the navy said.
The emergency happened on the second day of the biennial joint training exercise Talisman Sabre, which brings together 28,000 US and Australian military personnel over three weeks.
The US Navy and Marine Corps were working with Australian authorities to investigate the incident, the US Navy said.
Australian senator Larissa Waters, the influential Greens party's spokeswoman on the Great Barrier Reef, described the dumping of bombs in such an environmentally sensitive area as "outrageous" and said it should not be allowed.
"Have we gone completely mad?" she told ABC. "Is this how we look after our World Heritage area now? Letting a foreign power drop bombs on it?"
Graeme Dunstan, who is among the environmentalists and anti-war activists demonstrating against the joint exercises, said the mishap proved that the US military could not be trusted to protect the environment.
"How can they protect the environment and bomb the reef at the same time? Get real," Mr Dunstan said from the Queensland coastal town of Yeppoon, near the area where the war games are taking place.
The Great Barrier Reef Marine Park Authority, the government manager of the 133,360 square mile-protected zone, said identifying options for the "rapid recovery" of the bombs so that they could pose no risk to the marine park was "a high priority".
But the authority also said the ordnances posed a "low risk to the marine environment".
"Based on where the ordnance have been dropped in a location that is in water around 50 metres deep, about 30 kilometres from the nearest reef and 50 kilometres from the shoreline, the immediate impact on the marine environment is thought to be negligible," it said.
US 7th Fleet spokesman Lt David Levy said today the navy was, along with Australian authorities, reviewing the possibility of retrieving the ordnances.
"If the park service and the government agencies of Australia determine that they want those recovered, then we will co-ordinate with them on that recovery process," he said.
Lt Levy could not say whether the bombs were damaged or what the effect of long-term immersion in seawater could be.