Japan, the United States and South Korea affirmed Monday they will continue to closely work together in dealing with North Korea, amid the political chaos in Seoul brought about by President Yoon Suk Yeol's short-lived declaration of martial law.

During a meeting in Tokyo, senior officials from the three nations reiterated "serious concerns" over North Korea's advancing military cooperation with Russia, such as its recent dispatch of troops to help in the war against Ukraine, and its nuclear and missile development programs, according to Japan's Foreign Ministry.

The gathering came after a North Korea-Russia defense cooperation treaty took effect Wednesday, with the accord including a provision for mutual assistance if either country comes under attack.

The talks involved Hiroyuki Namazu, director general of the Japanese Foreign Ministry's Asian and Oceanian Affairs Bureau, Daniel Kritenbrink, U.S. assistant secretary of state for East Asian and Pacific affairs, and Cho Koo Rae, South Korea's vice foreign minister for strategy and intelligence.

The three countries underscored the importance of cooperation "even in the face of various complicating situations," the ministry said, alluding to last week's developments in South Korea.

They also discussed progress on initiatives to advance trilateral cooperation to disrupt North Korea's "malicious" cyber activities and reaffirmed their commitment to jointly seeking the immediate return of abductees, detainees and unrepatriated prisoners of war in the country, according to the U.S. State Department.

Yoon's declaration of martial law, which lasted only six hours from late Tuesday, triggered harsh criticism from the country's public and lawmakers. The president survived an opposition-led impeachment attempt over the weekend, but the ruling party has said he will not be actively governing ahead of his impending resignation.

Since Yoon, a conservative known for his hard-line stance toward North Korea, took office in 2022, the United States and its two close Asian allies have been boosting their defense collaboration. South Korea and Japan have also seen their bilateral ties improve after years of strained ties over wartime compensation and other disputes.