Japan and South Korea are concerned that North Korea could carry out another nuclear test on Oct. 10, when it celebrates the founding of the ruling Workers' Party.

Japan’s Defense Minister Itsunori Onodera warned Friday that the date coincides with the start of his country’s election campaigns, after Prime Minister Shinzo Abe dissolved the lower house of parliament and lawmakers called a snap election on Oct. 22. earlier this week.

North Korea often marks significant dates with tests of its weapons — last year, it carried out its fifth nuclear test on Sept. 9: the anniversary of the nation’s founding.

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Onodera urged caution. Pyongyang flew two intermediate-range missiles over Japan in August and earlier this month in response to joint U.S.-South Korean military drills and in defiance against diplomatic pressure.

“I understand it is an important anniversary for North Korea. We would like to maintain a sense of urgency,” Onodera told reporters of the upcoming date, according to Reuters.

On Thursday, South Korea’s national security adviser Chung Eui-yong said he expected action from North Korea around Oct. 10 and 18 — the beginning of China’s Communist Party Congress, Reuters reported. He did not give further details.

Meanwhile, South Korea's next ambassador to Russia said the Kremlin could play an important role in resolving the North Korean nuclear program issue, South Korean media reported Friday.

Woo Yoon-keun, who was appointed as the next envoy earlier this month, made the comments at a conference on relations between South Korea and Russia in Seoul.

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"Russia is the most important country in resolving emergency situations such as the North's nuclear problem that are in the way to the reunification of the Korean Peninsula and mediating between the interests of the U.S. and China," he said, according to the South’s news agency Yonhap.

China is North Korea’s most important ally, while China and Russia have forged a “special relationship.”

Chinese President Xi Jinping told reporters that China and Russia were each other’s “most trustworthy strategic partners” and that relations between the two were at their "best time in history,” after meeting with his Russian counterpart Vladimir Putin during a two-day visit to Russia in July.

Last month, President Trump said relations between the U.S. and Russia were at a "dangerous low" amid allegations that Russia interfered in the 2016 presidential election. South Korea is a key ally of the United States.

North Korea is facing increasing diplomatic pressure after it launched two intercontinental ballistic missiles, flew missiles over Japan and conducted its sixth and largest nuclear test since July.

The White House announced Friday that Trump will travel to Asia in early November, with stops in China, Japan, South Korea, Vietnam and the Philippines. Trade will be a major topic on the agenda.