Japan scrambled fighter jets 306 times in response to intruding Chinese aircraft in fiscal 2012 through March, a record high, the Defense Ministry’s Joint Staff said Wednesday.

It is the first time scrambles against Chinese planes have surpassed those against Russian aircraft. For fiscal 2012, scrambles against Russian aircraft totaled 248, an increase by one incident from the previous fiscal year.

Scrambles by Air Self-Defense Force jets against Chinese aircraft rose due to heightened tensions over the Japanese-administered Senkaku Islands in the East China Sea following Tokyo’s effective nationalization last September of the islet chain.

Japan has been prompted to scramble planes amid China’s increased military activities. China claims the islands, which it calls Diaoyu, and has in recent years pressed its claim, leading to bilateral friction.

The latest figure is almost double the previous record for scrambles against Chinese aircraft, at 156, and marks the highest level since the office began announcing figures by country in fiscal 2001.

Scrambling jets is an action taken in emergency situations by a country to intercept foreign aircraft looking to intrude into the country’s airspace.

Last December, a Chinese aircraft entered Japanese airspace over the Senkakus in the first such intrusion.

Since then, the ministry has bolstered the operations of its Airborne Warning and Control Systems planes as well as E-2C airborne early warning planes.

The ministry said it will keep close tabs on China’s actions.

Many of the Chinese aircraft were fighters, but the specific models are hard to determine just by looking at them, ministry officials said.

The number of times Japanese fighters scrambled in response to Chinese planes increased every three months from last April, first from 15 times rising to 54 times, then 91 times and ultimately 146 times.

Since one of China’s State Oceanic Administration airplanes entered Japanese airspace on Dec. 13, this kind of aircraft has approached to within about 100 km from the airspace over the Senkakus on eight occasions.

Buoyed by the rise in responses to Chinese aircraft, the total number of scrambles by Japan came to 567, marking the first time in 22 years the figure has surpassed 500.

The ministry has compiled statistics on scrambles from fiscal 1958. It was in fiscal 1984 at the peak of the Cold War when the greatest number of scrambles — 944 — occurred.