The headless bodies of 17 New Zealanders and five others executed by the Japanese during World War II are believed to have been found in Kiribati.

The victims were coastwatchers - Allied agents who worked behind enemy lines.

"We have a large pit with a number of bodies in it," New Zealand's High Commissioner in Kiribati, Rob Kaiwai, told Television NZ.

The unarmed coastwatchers were taken prisoner when the Japanese seized Tarawa in 1942. They were later beheaded.

Mr Kaiwai said the New Zealand operation to identify the lost men needed specialist help from experts such the United States Defence prisoner of war/missing personnel office, which has an experienced team of specialists with resources such as DNA testing.

"We don't want to move anything, touch anything, just expose them and have an expert come in and look at it," Mr Kaiwai said.