Concerns are growing in Tokyo after a Chinese government helicopter violated Japan's airspace around the Senkaku Islands, following a flight by a small Japanese civilian plane in the area and as Beijing sent government ships to the waters near the uninhabited islets in the East China Sea for more than 170 straight days.

On May 3, a China Coast Guard helicopter entered Japan’s territorial airspace around the Japanese-controlled, Chinese-claimed Senkaku Islands — marking just the fourth such incursion by a Chinese aircraft and first by a helicopter, according to the Defense Ministry.

As of Saturday, the Chinese side also had sent government ships to the area for 173 consecutive days.