China has introduced a law that will further integrate its coast guard into the military.
The amended law on the People's Armed Police Force went into effect on Sunday after the revision was approved by the Standing Committee of the National People's Congress the previous day.
The coast guard became part of the armed police force two years ago.
The law says the coast guard will conduct joint drills with the military. In an emergency, the coast guard will be put under the command of the Central Military Commission headed by President Xi Jinping or theater commands.
Chinese coast guard vessels have repeatedly intruded into Japan's territorial waters near the Senkaku Islands.
During an intrusion on May 8, Chinese vessels chased a Japanese fishing boat operating nearby.
The law's revision is likely to raise concerns among China's neighbors.
Japan controls the Senkaku Islands. China and Taiwan claim them. The Japanese government maintains the islands are an inherent part of Japan's territory in terms of history and international law.