The vessel was a Taiwan-registered fishing boat.
One person is dead and six missing, Japan's coastguard said Monday, after a boat capsized and was spotted in waters off the Tokyo-controlled Senkaku islets, which are also claimed by China.
It was unclear where the boat had initially capsized but on Sunday a Japanese navy patrol spotted it drifting in waters north of the islands, coastguard spokesman Keisuke Nakao told AFP.
The crew were one Taiwanese and six Indonesians, he added.
"At around 9:15 am (0015 GMT Monday), a body was found inside the cabin by divers, and an ID on the body suggests it was an Indonesian man," another spokesman Masaya Tokita said.
The coastguard has been searching the area with patrol ships and helicopters since receiving the information about the capsized boat on Sunday afternoon from the Maritime Self-Defense Force.
Coastguard officials said Japanese authorities were coordinating with their counterparts in Taiwan, which also lays claim to the Senkaku islets. Beijing calls the uninhabited territory the Diaoyu Islands.
Taiwan's foreign ministry confirmed in a statement that the vessel was a Taiwan-registered fishing boat, and was suspected to have capsized near one of the Senkaku Islands.
"The National Rescue Command Centre has contacted Taiwanese fishing boats near the site of the accident to assist in the search. Taiwan and Japan's coastguards have also dispatched ships for search and rescue," the statement said.
The boat's registered name is "Shin Charng Fa No 88," according to Taiwan's fisheries agency.
The vessel left northern Taiwan's Keelung port last Monday, and had contacted a Taiwanese fishing boat nearby for help on Sunday, the agency added.
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