Japanese fighter jets have been scrambled 944 times in the past year - the most since the cold war

Japan's air force said jet fighter scrambles have reached a level not seen since the height of the cold war three decades ago as Russian bombers probe its northern skies and Chinese combat aircraft intrude into its southern air space.

In the year ending March 31, Japanese fighters scrambled 944 times, 16 per cent more than the same period the previous year, the country's Self Defence Force said. That is the second-highest number of encounters ever recorded over the 12-month period since records began in 1958 and only one less than a record 944 scrambles in 1984.

"It represents a sharp increase" an SDF spokesman said.

While not a direct measure of Russian and Chinese military activity, the numbers nonetheless point to an increase in operations by Japan's two big neighbours.

Japan is upping defence spending to buy new equipment, including longer-range patrol aircraft, cargo jets, helicopter carriers and troop carrying Boeing V-22 Ospreys and Lockheed Martin F-35 stealth fighters.

Russian bombers and patrol planes often enter Japan's air space close to Japan's northern Hokkaido island and close to four smaller islands which are claimed both by Japan and Russia. That territorial dispute has prevented Japan and Russia from concluding a formal peace treaty.