Bodies of seven men and three women were found floating after the boat went missing with 26 people on board.
All 10 people found so far from a Japanese tour boat missing off the country’s northern coast have been confirmed dead, the coast guard said.
The announcement came on Sunday, a day after the boat went missing with 26 people on board during a cruise off the main northern island of Hokkaido.
The bodies of seven men and three women were found floating in the water and were brought to a hospital, where the deaths were confirmed. Seven passengers remain unaccounted for, after nine were rescued earlier.
The nine were found unconscious in the water around Hokkaido’s Shiretoko Peninsula and taken to hospital, broadcaster NHK reported.
Rescue efforts continue despite high waves, to find the remaining passengers, including two children, and the boat.
Footage on NHK showed one of the rescued people arriving on a helicopter and being transferred to an ambulance on a stretcher, while rescuers held up blue plastic shields for privacy.
Sunday’s rescue came after nearly 19 hours of intense search involving six patrol boats, several aircraft and divers. The coastguard said the search continued through the night.
The Kazu 1 made an emergency call in the early afternoon on Saturday, saying the ship’s bow had flooded and it was beginning to sink and tilt while travelling off the western coast of Shiretoko Peninsula near the northern island of Hokkaido, the coastguard said.
It was last heard from about two hours later, when it contacted its operating company to say it was keeling at a 30-degree angle, according to Kyodo News agency.
The crew said those on board were wearing life jackets.
There were 24 passengers and two crew members on board. Two of the passengers were children.
Average April sea temperatures in Shiretoko National Park, which was designated a UNESCO World Heritage Site in 2005, are just above freezing.
Sightseeing boat trips in the area are popular for visitors hoping to spot whales, birds and other wildlife, as well as drift ice in the winter.
Prime Minister Fumio Kishida, who was attending a two-day summit in Kumamoto in southern Japan, cancelled his programme for the second day and returned to Tokyo. He told reporters in the early hours of Sunday that he instructed officials “to do everything they can for the rescue”.
The cause of the accident is still under investigation, but experts suspect the boat ran aground and was damaged.
High waves and strong winds were observed in the area around noon on Saturday, according to a local fisheries cooperative. Japanese media reports said fishing boats had returned to port before noon because of the bad weather.
NHK said there was a warning for high waves of up to 3 metres (10 feet).