Russian President Vladimir Putin has emphasized that waters around four Russian-held islands claimed by Japan are strategically important. He pledged to use all possible means to defend the area.

Putin signed an executive order approving a new Maritime Doctrine on Sunday, when a celebration was held in St. Petersburg to mark Russia's Navy Day.

Putin said in a speech that the doctrine clearly defines the boundaries and areas of Russia's national interests.

He added that vital strategic areas include the Black Sea, the Sea of Okhotsk, and waters around the Kuril Islands. The president said Russia will protect those areas by all means.

What Russians call the Kuril Islands include four Russian-controlled islands that are claimed by Japan.

Japan calls the islands the Northern Territories. The Japanese government maintains the islands are an inherent part of Japan's territory. It says the islands were illegally occupied after World War Two.

The new doctrine divides the areas of Russia's interests in the world's oceans into three categories --"vitally important," "important" and "others." It categorizes the waters around the Northern Territories as "important."

The document also lists the main challenges and threats to Russia's national security, including territorial claims over its islands.

Other security threats mentioned in the doctrine include what it calls the US strategic policy to dominate the world's oceans, and the expansion of the NATO military infrastructure towards Russian borders.

The document says Russia may use mostly diplomatic or economic measures to defend its national interests in the areas it defines as "important," but may use military forces depending on the situation.