BEIJING - China on Thursday warned Japan against “playing with fire” in the contested waters of the South China Sea, after Tokyo announced it may patrol alongside the US in the region.

China also sent fighter planes for the first time over a strait near Japan on Monday as part of a group of more than 40 jets headed to train in the West Pacific.

The move followed remarks by Japanese Defence Minister Tomomi Inada this month that Tokyo would increase its engagement in the South China Sea through joint training with the US Navy, exercises with regional navies and capacity-building assistance to coastal nations. The Chinese defence ministry said the aim of the announcement was “to mess up the South China Sea situation and try to gain interests from the troubled waters.”

“If Japan wants to conduct any joint patrol or joint exercises in waters administered by China, it is just like playing with fire, and the Chinese military will not sit and watch,” ministry spokesman Yang Yujun told a regular press briefing.

Beijing asserts sovereignty over almost all of the South China Sea, dismissing rival partial claims from its Southeast Asian neighbours. It rejects any intervention by Japan in the waterway.

In recent months Japanese Prime Minister Shinzo Abe has criticised China for rejecting a July ruling by an international tribunal, which said Beijing’s extensive claims to the waters had no legal basis.

Tokyo, a key US ally, is also strengthening defence ties with other countries in the disputed region. Japan and China are already at loggerheads over a longstanding territorial row in the East China Sea.

That dispute relates to uninhabited islets controlled by Japan known as the Senkakus in Japanese and the Diaoyus in Chinese.

Beijing again warns against US

anti-missile system in S Korea

China “means what it says” when it says it will consider countermeasures against the planned US deployment of an advanced anti-missile system in South Korea, the defence ministry said on Thursday.

China, North Korea’s neighbour and lone major ally, has repeatedly expressed anger at the United States and South Korea for their decision to deploy the US Terminal High Altitude Area Defence (THAAD) system in the South to counter missile and nuclear threats from North Korea. The South Korean defence ministry said it would announce a new location for the system on Friday, after opposition from residents for the initial site choice.

Chinese Defence Ministry spokesman Yang Yujun said China’s opposition to THAAD was clear.

“We will pay close attention to relevant developments, and consider taking necessary actions to protect national strategic security and the regional strategic balance,” Yang told a monthly news briefing. “What needs to be stressed is that Chinese people mean what they say,” he added, without elaborating.

Beijing worries the system’s radar will be able to track its own military capabilities, and that the deployment will do nothing to lower temperatures on the Korean peninsula. Russian has expressed similar opposition.

North Korea, which has threatened a “physical response” against the THAAD decision, has conducted a series of military technology tests this year, including a fifth nuclear test this month, in defiance of UN Security Council sanctions that were tightened in March.