TOKYO -- China has been piling diplomatic, military and economic pressure on Japan for months. Increasingly, Russia and North Korea are joining in, too.
Russian President Vladimir Putin for the first time visited the remote southern Kuril Islands in Russia's far east on Thursday, a chilly archipelago that Japan claims as its own. Russia seized the islands from Japan in the dying days of World War II and a dispute over their sovereignty has bedeviled relations between Moscow and Tokyo ever since.
"It hurts the feelings of the Japanese people and is absolutely unacceptable," Japanese Prime Minister Sanae Takaichi said of Putin's visit to the island of Iturup, known as Etorofu in Japanese.
She told reporters in Tokyo, "I hope the Russian side takes the gravity of this matter very seriously."
The island quarrel is the latest sign of strained relations between Japan on one side and China, Russia and North Korea on the other.
The friction highlights the growing displeasure among Japan's nuclear-armed neighbors at Tokyo's plans to boost its defense capabilities and strengthen its military ties with the U.S., analysts say.
The visit by Putin, who was photographed eating fish roe at a processing plant and chatting to employees, comes just days after Japan protested to North Korea over the firing of a ballistic missile into waters west of Japan. The launch took place on the day Japan was commemorating the 81st anniversary of the U.S. atomic bombing of Hiroshima.
And it follows months of diplomatic friction with Beijing, which was angered by Takaichi's remark last year that Japan could get dragged into any conflict over Taiwan, a self-ruled democracy Beijing says is part of China and has pledged to absorb, by force if necessary. In retaliation, China has canceled tourist flights to Japan from China and throttled Japanese firms' access to critical minerals needed in manufacturing.
Chinese officials have for months accused Japan of rekindling the spirit of Japanese militarism that fueled its brutal wartime conduct, a charge since picked up by North Korea and Russia.
Viktor Liina, commander of Russia's Pacific Fleet, said on Wednesday the Japanese "military-political leadership" has set the country on course toward "open militarization," according to Russian state media.
"The language is very similar," said James Brown, an expert in Japan-Russia relations at Temple University in Tokyo. "It does seem to be about deliberately making common cause with China."
Tokyo says its increased military spending is in response to a worsening security environment surrounding Japan, a deterioration it blames on China, Russia and North Korea.
Japan recently tested a U.S.-made Tomahawk cruise missile, and it participated in U.S.-led military exercises earlier this year. Japan has been steadily fortifying its southwestern islands with missiles and garrisons to defend against attack.
In a report published this month, Japan's defense ministry said Japan faces its most severe and complex set of security challenges in 80 years.
Among Japan's concerns, the report listed China's aggressive pursuit of its expansive maritime claims, Russia's invasion of Ukraine and North Korea's nuclear advances. The report cited growing military cooperation between the three countries as a heightened security risk.
The report also described how Russia has deployed antiship missiles, warplanes and other military equipment to the Kuril Islands visited by Putin.