TOKYO — Chinese military fighter jets have been operating near the disputed Senkaku Islands in the East China Sea since late May and one of them flew in an area within 50km of Japan’s territorial airspace around the islets, said a Japanese government source over the weekend.

Tokyo scrambled Air Self-Defence Force (ADSF) fighter jets against the Chinese aircraft, said the source, adding it is “abnormal” for Chinese aircraft to approach to such a close distance.

Chinese military aeroplanes have neared the islets more than three times since late May, added the source.

During the April to June period, Japan scrambled ASDF fighter jets against Chinese aircraft approaching its airspace a record 199 times, breaking the previous record of 198 set over the preceding three months, said the Japanese Defence Ministry.

Japan’s defence white paper released by the ministry earlier this month criticised China’s activities in the sea as “high-handed” unilateral action attempting to alter the status quo by force.

Mr Kunio Orita, a former head of the ASDF Air Support Command, published a report online in late June, saying an ASDF plane, which had been scrambled, left the area while employing a counter-measure to avoid a possible missile attack. The Defence Ministry has denied the report.

China has been stepping up pressure on Japan over the disputed Senkaku Islands, which are called Diaoyu in Chinese. Hundreds of fishing boats and more than a dozen coastguard vessels have been spotted recently in the area, encroaching at times on what Japan sees as its territorial waters.

Ties between the major trading partners suffered a sharp deterioration in 2012 when Japan bought three of the East China Sea islands from a private landlord.

China is also engaged in separate territorial disputes in the South China Sea.

Beijing claims almost the entire South China Sea, through which more than US$5 trillion (S$6.7 trillion) of trade moves annually. Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims in the sea, believed to be rich in energy deposits.

Beijing has conducted massive reclamation in the disputed waterway, with a US-based think-tank releasing images last week showing what appears to be Beijing building military aircraft hangars on disputed reefs.

An arbitration court in The Hague ruled on July 12 that China had no historic title over the busy waterway and had breached the Philippines’ sovereign rights there.

The decision infuriated Beijing, which dismissed the court’s authority to rule on the matter.

Last week, Japan and the Philippines joined forces to call on China to observe the rule of law in resolving maritime disputes.

“We have agreed that in the pursuit of the solution to the conflict in the maritime area, it is important to base ourselves on the rule of law and resort to peaceful means and not the use of force or coercion,” said Japanese Foreign Minister Fumio Kishida.

“We invoke and urge China to make sure that maritime security and the rule of law must completely and uncompromisingly be respected,” Philippine Foreign Minister Perfecto Yasay had added.

Meanwhile, Japanese daily Yomiuri has reported that the government will develop land-to-sea missiles with a range of 300km to protect the nation’s isolated islands, including Senkaku, without saying where it heard the information.

The government will aim for deployment about the end of March 2024, said Yomiuri. AGENCIES