The Air Self-Defense Force scrambled fighter jets 160 times against Chinese aircraft approaching Japanese airspace in the nine months between April and December, surpassing the record high 156 scrambles made in all of fiscal 2011, the Defense Ministry, which started disclosing such data by country in 2001, said Thursday.

In the nine months, ASDF fighter jets were scrambled 349 times in total, up 14 from the same period in fiscal 2011, the ministry’s Joint Staff Office said.

Although most scrambles were against Russian aircraft, numbering 180, the increase was mostly due to a rise in Chinese intrusions, according to the ministry data.

The majority of Chinese aircraft flew over the East China Sea around the Nansei Islands, which include the disputed, Japan-controlled Senkaku islets, according to the ministry.

“When compared with the same period last fiscal year, it was a slight increase. But (regarding scrambles against) Chinese (planes), the number is getting high,” Gen. Shigeru Iwasaki, head of the Self-Defense Forces, told media outlets in Tokyo.

The increase is due to increasing Chinese military activities in recent years, Iwasaki said, adding the surge cannot be simply linked to the mounting tensions over the Senkaku Islands. China claims the islets, which it calls Diaoyu.

Since a Chinese government aircraft intruded into Japanese airspace for the first time over the Senkakus on Dec. 13, the ministry has been on alert, dispatching E-2C early warning aircraft and airborne early warning and control system aircraft to Okinawa to monitor intrusions as quickly as possible.