Two U.S. fighter jets dropped four unarmed bombs into Australia's Great Barrier Reef Marine Park last week when a training exercise went wrong, the U.S. Navy said, angering environmentalists.

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 on Tuesday, the U.S. 7th Fleet said in a statement Saturday.

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 northeast coast.