Japan’s Self Defense Forces are preparing for the possibility that North Korea may launch a large-scale infiltration attempt as part of a terrorist attack.

Yonhap news agency quoted unidentified sources in Japan’s military headquarters as saying its armed forces drafted a defensive strategy on the premise of an infiltration attempt by up to 2,500 North Korean special forces using spy ships and submarines.

The strategy, Yonhap said, calls for placing Japanese troops to guard 35 key facilities including, government buildings, nuclear reactors, oil storage tanks and U.S. military bases.

It said the Japanese military is also stressing that Tokyo should expand the number of its troops to 230,000 from the current 150,000 in order to adequately deal with all outside threats.