Japan\'s Prime Minister Shinzo Abe on Thursday voiced concern over the flight of a Chinese military plane near the Japanese southern islands on the previous day, calling it an unusual act. \"It was an unusual action that we have never seen before. We will keep monitoring the situation with great interest, Abe told reporters before leaving Tokyo for a 3-day trip to Malaysia, Singapore and the Philippines. \"I\'d like to share with Asian leaders an understanding that we should establish an order ruled by law, not by force,\" Abe said. Malaysia, Philippines, Vietnam and Brunei also dispute China\'s claim to islands and waters in the South China Sea. On Wednesday, Japan scrambled its fighter jets after a Chinese early warning aircraft flew through international airspace near the Japanese southern islands, Defense Minister Itsunori Onodera said. The Chinese plane did not enter Japanese airspace, but passed over open waters between Okinawa\'s main island and the smaller Miyako Island for the first time. Onodera said t indicates China\'s growing willingness toward maritime expansion in the area. Japan and China are at odds in a dispute over the sovereignty of the uninhabited islands in the East China Sea. The Japan-administered Senkaku Islands, known as Diaoyu in China and Tiaoyutai in Taiwan, are claimed by the three countries. The small chain of uninhabited rocky islands lie in rich fishing grounds and waters thought to contain large deposits of oil and natural gas. Relations between the world\'s second and third-largest economies have sharply deteriorated since Tokyo\'s nationalization of three of the five major islands in September 2012 through purchase from a private Japanese owner. The Chinese government ships have repeatedly entered the waters around the islands since Tokyo\'s acquisition of the islets.