A group that searches for the remains of American troops lost in past battles has found what officials believe are the graves of more than 30 Marines and sailors killed in one of World War II’s bloodiest battles.

The remains were found on the remote Pacific atoll of Tarawa, the scene of a fierce battle with the Japanese in November 1943.

More than 1000 American troops died in the three-day Battle of Tarawa.

The non-profit group that found the remains, History Flight, works with the US defence department and Kiribati – of which Tarawa is part – to search for the dead soldiers.

History Flight president Mark Noah said the remains were believed to belong to troops from the 6th Marine Regiment.

The American marines and sailors died on Tarawa after their boats got stuck on the reef when the US assault was launched at low tide. Many were mown down by Japanese machine guns, while those who made it to the beach faced brutal hand-to-hand combat.

AP said the US military buried its men in makeshift cemeteries where they fell. The markers were later removed when runways and other infrastructure was hastily built to help the US push further west across the Pacific toward Japan.

US marines in battle against Japanese troops on Tarawa in November 1943. Photo: Getty

Dr John Byrd, director of the US defence force’s MIA Accounting Agency, told America’s Associated Press that the remains would be recovered and flown to Hawaii. Military forensic anthropologists will then work to identify them using dental records, DNA and other clues.

The Kiribati government allowed History Flight to demolish an abandoned building in its search – most of the graves were beneath it.

Many are also below the water table, meaning History Flight workers must pump water from the site each day to excavate.

History Flight, which is based in Virginia, has recovered the remains of 68 individuals, as well as more than 200 sets of partial remains from Tarawa since 2015. Mr Noah estimates another 270 remain undiscovered on the atoll.

-with agencies