Seoul, South Korea (CNN)At least eight Russian and Chinese warships have been spotted in the seas near Japan this week, another sign of the apparent pressure the two partners have been putting on Tokyo as relations deteriorate over Ukraine and Taiwan respectively.
Japan tracks eight Russian and Chinese warships near its territory
Japan's Defense Ministry on Tuesday said its forces had observed five Russian warships led by an anti-submarine destroyer steaming through the Tsushima Strait, which separates Japan and South Korea.
The five-ship Russian flotilla has been near Japanese islands for a week, from Hokkaido in the north to Okinawa in the south, the ministry said in a news release.
Meanwhile, at least two Chinese warships and a supply ship were spotted Tuesday in the Izu Islands, about 500 kilometers (310 miles) south of the capital Tokyo. One of those ships appeared to be the Lhasa, a Type 55 guided-missile destroyer and one of China's most powerful surface ships.
The ministry said that group has been operating in waters near Japan since June 12.
"This is an obvious show of force from both Russia and China," said James Brown, associate professor of political science at Temple University in Tokyo.
"These activities are a major worry for Japan. Not least, tracking the movements of both Russian and Chinese military forces are a strain on the resources of the Japan Self Defense Forces."
There was no claim from Tokyo that the Russian and Chinese naval groups were coordinating their actions, like they did last October when a total of 10 Russian and Chinese warships jointly participated in exercises in which they circumnavigated much of the Japanese archipelago.
More recently, as Japanese Prime Minister Fumio Kishida hosted a summit of the leaders of the United States, Australia and India in Tokyo, the Chinese and Russian air forces conducted joint strategic air patrols over the Sea of Japan, the East China Sea and the western Pacific Ocean, in what the Chinese Defense Ministry called part of an annual military cooperation plan.
Brown said Kishida's hosting of that summit was just one reason Beijing would want to show its displeasure with Tokyo.
"Beijing has been angered by Japanese statements regarding the security of Taiwan, which the Chinese Communist Party considers a domestic matter," Brown said.
In fact, it was at the Tokyo summit that President Joe Biden said the United States would intervene militarily if China attempts to take Taiwan by force. The White House later walked back that comment, but the US does maintain a powerful military presence in Japan -- troops that could come into play in any conflict over Taiwan.
Taiwan and mainland China have been governed separately since the defeated Nationalists retreated to the island at the end of the Chinese civil war more than 70 years ago.
But China's ruling Chinese Communist Party views the self-ruled island as part of its territory -- despite having never controlled it.
Beijing has not ruled out military force to take Taiwan, and Japan sees conflict across the Taiwan Strait as a threat to its security.
Meanwhile, Moscow has been angered by Tokyo's support for Ukraine after Russian forces invaded their European neighbor nearly four months ago, Brown said. That support has included imposing sanctions on Moscow and expelling Russian diplomats.
"Russia therefore wishes to use its military power to intimidate Japan in the hope that this will deter Tokyo from imposing further such measures," Brown said.