At least 10 people have been killed after a tourist boat went missing off the northern Japanese island of Hokkaido, the Japan Coast Guard says.

They say the search is continuing in frigid waters for 16 others who were on board the Kazu 1 vessel.

Contact with the boat was lost after it said it was taking on water at 13:15 local time (04:15 GMT) on Saturday.

The Kazu 1 is believed to have been on a three-hour sightseeing voyage around the Shiretoko Peninsula.

The area is a designated UNESCO world heritage site, and boat trips are popular with tourists hoping to spot whales and sea lions as well as brown bears on the rocky beaches.

The crew managed to signal that the vessel was tipping at a 30-degree angle and starting to sink, according to Japanese media.

Patrol boats and police and military aircraft were immediately dispatched to find the vessel. Local fishing boats were also taking part in the search operation.

Of the 26 on board, two were crew and two were children.

Earlier reports suggested that several people were pulled out of the waters - but it is unclear if they are among the confirmed 10 victims.

Waves in the area had been high and local fishing boats had apparently decided to return to port by mid-morning.

The crew reportedly said that all those on board were wearing life jackets.

But temperatures in the area can dip as low as 0C (32F) when night falls.