Japan's Coast Guard continues to search for 12 people who remain missing three months after a tour boat sank off the northern island of Hokkaido.

The "Kazu I" vessel carrying 26 people, sank on April 23 in waters off the Shiretoko Peninsula. Fourteen people have been confirmed dead, while the rest remain missing.

From May through June, Russian authorities informed Japan that three bodies had been found along the coasts of Kunashiri Island and Sakhalin Island.

Tests conducted by the Russian side show that the DNA of the bodies matched DNA samples of two passengers and a crewmember of the sunken boat.

Arrangements are under way on the handover of the bodies through diplomatic channels between Japan and Russia.

Sources say the parties failed to reach agreement on a plan to hand over the bodies halfway between the main island of Hokkaido and Kunashiri.

They say negotiators are now considering whether it is possible for a Japanese vessel to be sent to retrieve the bodies, among other options. However, details have yet to be worked out.

Kunashiri is one of four Russian-controlled islands Japan claims as an inherent part of its territory.