Japan has expressed its “serious concern” following the close passage of Chinese and Russian naval vessels near its southern islands on Thursday.

The development came just a day prior to its leader is expected to participate in a summit with counterparts from South Korea and the United States, where discussions about escalating tensions in the Indo-Pacific are on the agenda.

A fleet of six Chinese ships, including missile destroyers, along with five Russian vessels, some of which were also destroyers, traversed the waters between Japan’s Okinawa Island and Miyako Island. Subsequently, the flotilla proceeded towards the East China Sea, as reported by Japan’s defence ministry.

Notably, this marks the first instance of Russian and Chinese naval vessels jointly navigating through this specific maritime route. It is important to underline that the ships did not violate Japan’s territorial waters.

Meanwhile, against the backdrop of heightened concerns over Russian and Chinese military activities in the region, a collaborative naval exercise involving the United States, Japan, and Australia is scheduled for Wednesday. This initiative is being undertaken as tensions continue to escalate in the South China Sea.

China is renewing its criticism of this weekend’s summit among the leaders of the U.S., Japan and South Korea, saying no country should “seek its own security at the expense of the security interests of others and of regional peace and stability.”

“The international community has its own judgment as to who is creating contradictions and increasing tensions,” Foreign Ministry spokesperson Wang Wenbin told reporters at a daily briefing Friday.

“Attempts to form various exclusive groups and cliques and to bring bloc confrontation into the Asia-Pacific region are unpopular and will definitely spark vigilance and opposition in the countries of the region,” Wang said.

The summit at the rustic Camp David presidential retreat seeks to further tighten security and economic ties between Japan and South Korea, two nations whose historically frosty relations have rapidly thawed over the last year as they share concerns about China’s assertiveness in the Pacific and North Korea’s persistent nuclear threats.

China is extremely sensitive to any moves it perceives as seeking to contain its rise to dominance in Asia and has traditionally counted on the historical enmity between Tokyo and Seoul to keep its rivals divided and weaken the U.S. system of regional alliances.

Beijing has made clear the current rapprochement between the two was something it very much did not want to see and its top diplomat, Wang Yi, last month made a clumsy and much-criticized appeal to racial-cultural similarities between Chinese, Japanese and Koreans as an alternative to partnering with the West.

“No matter how yellow you dye your hair, or how sharp you make your nose, you’ll never turn into a European or American, you’ll never turn into a Westerner,” said Wang, a former foreign minister who now heads the ruling Communist Party’s foreign affairs commission.

“One needs to know where one’s roots are,” Wang added.

President Joe Biden is looking to use the summit to urge South Korean President Yoon Suk Yeol and Japanese Prime Minister Fumio Kishida to firmly turn the page on their countries’ difficult shared history.

The Japan-South Korean relationship is a delicate one because of differing views of World War II history and Japan’s colonial rule over the Korean Peninsula. Past efforts to tighten security cooperation between Seoul and Tokyo have progressed by fits and starts.

Expected major announcements include plans to expand military cooperation on ballistic missile defences and make the summit an annual event.

In the face of deteriorating ties with Washington, Seoul and Tokyo, China has grown closer to Russia, with whom it declared a “no-limits” partnership just prior to President Vladimir Putin’s full-on invasion of Ukraine last year.

Japan’s Defense Ministry on Friday said it scrambled fighter jets after spotting two Russian IL-38 reconnaissance aircraft flying back and forth over the Tsushima Strait in southwestern Japan.

A day earlier, the ministry said Japan spotted a fleet of 11 Chinese and Russian navy ships crossing waters between the southern Japanese islands of Okinawa and Miyako.

The fleet comprised six Chinese and five Russian warships, many of which had taken part in what they called a joint patrol in July when they sailed through the Soya Strait between the northern main island of Hokkaido and Sakhalin, the Japanese Defense Ministry said Thursday. The ministry views the repeated joint military activities by the two countries around Japan as aimed at demonstrating their combined threat against Japan, and expressed concern to both China and Russia, Kyodo News reported.

Asked about the activities, Wang said, “It conforms to international law and international practice for the Chinese and Russian vessels to conduct normal patrols.”

China has also sought stronger relations with developing nations in Africa and Central and South America and President Xi Jinping will be attending next week’s summit in Johannesburg of the BRICS bloc linking Brazil, Russia, India, China and South Africa.

With inputs from agencies.