It has emerged that an aborted training mission between US and Australian armed forces resulted in two American jets dropping four bombs on the Great Barrier Reef Marine Park last week.

Two of the bombs were unarmed, two were inert and none of the four exploded.

According to the US Navy, the bombs had to be dropped in the water after the training mission was aborted due to the target, the Township Island bomb range, being deemed unsafe.

"It was not safe to drop the bombs. There were civilian boats right below them," Commander William Marks of the US Seventh Fleet, told the Australian Broadcasting Corporation.

Marks said the Harrier jets carrying the bombs were low on fuel and needed to return to the aircraft carrier, but they were unable to land while equipped with the bombs.

The planes jettisoned the bombs about 16 nautical miles south of Bell Cay in the Great Barrier Reef Marine Park, a UNESCO World Heritage Site and popular tourist destination in Australia.

According to the Navy, the bombs were dropped in about 200 feet of water in a deep channel away from the reef itself in order to "minimize damage." The unexploded bombs, the Navy said, pose no threat to shipping or navigation in the waters.

"We are coordinating with Australian officials to ensure an appropriate navigation notice is issued until charts can be updated showing the location of the unexploded ordnance," the Navy said in a statement obtained by Reuters.

The aborted mission was part of a joint training initiative known as Talisman Saber, a biennial occurrence which began this year on July 15 and will end on Aug. 5.

Whether or not the bombs are retrieved is up to the Australian government, Mother Nature Network reported, adding that in similar cases in the past the bombs have left where they landed The US Navy has offered Austrailia any assistance it requires, should it choose to retrieve the bombs. 

While the military is downplaying the issue, others are up in arms. 

"Have we gone completely mad? Is this how we look after our World Heritage area now? Letting a foreign power drop bombs on it?" Australian Green Party senator Larissa Waters said, according to MNN.

Speaking with The Guardian, Waters said that when she first heard about the incident she "thought it was a joke."

"This training area is exempt from protections for the reef which is worrying when there is such huge weaponry and munitions involved," she said. "It's simply not an appropriate place for war games and I will be raising the matter in Senate estimates. This is a huge safety issue, it's outrageous there wasn't better safety with the boats involved, especially given that this area is a tourist Mecca."

Reuters reports that the Great Barrier Reef Marine Park brings in about $6 billion dollars a year to the Australian economy.