Japan scrambled jets to intercept Chinese aircraft near the Diaoyu Islands a record 160 times in the nine months between April and December.
The figure - four more than in the previous 12 months - underlines the simmering tensions around the disputed archipelago, called the Senkakus by Japan, in the East China Sea.
Japan's Ministry of Defence said its Air Self-Defence Force (ASDF) aircraft were required to meet potential intruders 349 times during the period, 14 more than the previous year.
Russian aircraft remained the ASDF's most numerous opponent with 180 incidents, the ministry said.
But the overall increase was due to China ramping up its presence around the disputed islands. Tensions increased on December 13 when a unit of six F-15 fighter jets was scrambled from Okinawa.
The move came after a surveillance aircraft belonging to the Chinese Oceanic Administration was sighted close to the largest of the chain of uninhabited islands.
It was the first such incident involving a Chinese government aircraft since Japanese monitoring began in 1958, the ministry said.
The same day, four Chinese patrol vessels entered waters close to the islands.
Immediately after a Japan coastguard patrol vessel had identified the Chinese aircraft over the islands, Tokyo filed an official protest with Beijing.
Tokyo is considering activating an airbase in the Nansei islands that would allow ASDF aircraft to intercept aircraft approaching the disputed islands more rapidly.