The Kremlin said on Friday it had a sovereign right to carry out work in the Sea of Okhotsk off Russia's far eastern coast after a Japanese official objected to Moscow conducting a geological survey there.

Japan's Chief Cabinet Secretary Yoshihide Suga described Russia's survey as unacceptable and in conflict with Tokyo's position on four Russian-held islands claimed by Japan, the Japan Times cited him as saying.

"Russia has a sovereign right to carry out any research on its territory," said Kremlin spokesman Dmitry Peskov during a conference call on Friday.

The geological survey in the Sea of Okhotsk, near the disputed islands, began on June 18 and is set to last for three months, Russian news agencies reported.

Japan calls the four Russian-held islands, off its main northern island of Hokkaido, the Northern Territories. Known in Russia as the Southern Kuriles, the islands were seized by Soviet forces in the closing days of World War Two.

The territorial issue has blighted relations between Russia and Japan for decades and has prevented them from signing a formal peace treaty ending World War Two.

Reuters