The Japanese coastguard is searching for an island that has gone missing off Hokkaido.

The island of Esanbe Hanakita Kojima, which was formally named in 2014 by Tokyo in an effort to reinforce its legal control over hundreds of outlying islands and extend its exclusive economic zone, appears to have sunk without trace.

It was last the subject of a formal survey in 1987, when records indicated its high point was approximately 1.4 metres above the average sea level, the Asahi newspaper reported.

Lying about 500 metres off the coast close to the village of Sarufutsu, the island had served to extend Japan’s EEZ a similar distance out to sea in an area where Japanese waters butt up against Russian territory.

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A short distance to the east, Russia controls a chain of islands that Moscow refers to as the Kuril Islands that were seized in the closing days of the second world war. Tokyo still lists the islands as the Northern Territories on its maps and has been campaigning for their return since 1945.

Officials believe that the island has been gradually eroded by the elements, including pack ice that covers the area in the depths of winter, and has slipped beneath the surface.

The coastguard has been tasked with carrying out a survey of the area to see if the remnants of the island remain. Even if the base of the islet can be located, it will no longer meet the international legal definition of an island and the EEZ will consequently shrink – albeit marginally.

Esanbe Hanakita Kojima was one of 158 uninhabited islands given names by the government in 2014 to reinforce Japan’s maritime claims.