OSHIMA, Japan (AFP) - Frogmen were on Friday scouring waters off the coast of a Japanese island where landslides buried houses when a huge typhoon rolled through, as the death toll reached 24.

Coastguard joined the grim search for the 27 people still unaccounted for after a mountainside collapsed on the island of Oshima, 120 kilometres south of the Japanese capital.

Troops, firefighters and police were on Friday continuing their search on land, using shovels to move huge volumes of earth that swamped homes.

Meanwhile, the body of one of two elementary schoolchildren believed to have been near a beach in Kanagawa when the storm hit has been found, a local official said.

The other child and a man in Chiba were still listed as missing.

Typhoon Wipha, the most powerful in ten years, veered up the coast of the Japanese archipelago overnight Tuesday into Wednesday.

The eye of the storm remained offshore but the strong winds and heavy rain that it brought wreaked devastation on Oshima, one of a number of far-flung islands that are administratively part of metropolitan Tokyo.

Tokyo governor Naoki Inose, who visited rescue workers on Thursday, urged them to do their utmost to find anyone who was still alive, Jiji Press reported.

"The 72-hour 'golden rescue period' is going to be over soon," he said, referring to the time after which it is thought survival is unlikely. "I expect you to do everything you can."

Prime Minister Shinzo Abe was readying to visit the island on Sunday where he would board a helicopter to see the scars left by the storm before visiting evacuation centres, public broadcaster NHK reported.

Disaster management minister Keiji Furuya and defence minister Itsunori Onodera were expected to go on Saturday, reports said.