ISTANBUL 

Japan has formally protested to Russia after Moscow restricted navigation in the waters surrounding disputed islets, said a senior official in Tokyo on Thursday.

The disputed islands -- known as Northern Territories in Japan and Southern Kurils in Russia -- have prevented Moscow and Tokyo from signing a postwar peace treaty.

Chief Cabinet Secretary Yoshimasa Hayashi said during a press conference that Tokyo used diplomatic channels to convey its protest to Russia.

The temporary restriction affects the passage of foreign military and government ships in the waters surrounding the islands, Kyodo News reported.

The four islands (Kunashir, Iturup, Shikotan, and Habomai) are disputed by Moscow and Tokyo.

Hokkaido Island in Japan and the Kamchatka Peninsula in Russia's Far East are on opposite sides of the Pacific Ocean.