TOKYO (Kyodo) -- The Japanese government on Saturday underscored the need to cooperate with South Korea and maintain close communication amid the tough regional security environment, as South Korea's ongoing political turmoil resulted in the passage of an impeachment motion against President Yoon Suk Yeol.

Prime Minister Shigeru Ishiba, speaking to reporters during a visit to northeastern Japan prior to the vote, said the importance of the bilateral ties "will not change at all." Defense Minister Gen Nakatani said later that South Korea is "an important neighboring country and partner in tackling various challenges the international community faces."

"As the regional security environment becomes more severe, we would like to continue to closely communicate with South Korea," Nakatani also said in the southern island prefecture of Okinawa.

South Korea's political chaos, triggered by Yoon's short-lived declaration of martial law on Dec. 3, is being closely watched as it could negatively affect trilateral collaboration also involving the United States, and undermine the deterrence against North Korea, which continues its nuclear and missile development.

While a Japanese government source played down concerns that the development will affect ties between Tokyo and Seoul, the government is apparently hoping the situation will stabilize as soon as possible.

With the impeachment motion's passage, Yoon's presidential authority has been suspended, and Prime Minister Han Duck Soo has assumed the role of acting president. Yoon will be removed from office if the impeachment is approved by the Constitutional Court within 180 days.

"It will take time to build a new personal relationship among leaders toward Japan-U.S.-South Korea cooperation," a Japanese government source lamented.

"The replacement of Yoon may mean a change in South Korea's cooperative stance," a senior Japanese Foreign Ministry official said, referring to the conservative president who has put emphasis on the Seoul-Tokyo relationship and taken a hawkish stance toward Pyongyang.

Since Yoon took office in 2022, security cooperation among the United States, Japan and South Korea has strengthened. He has also helped ease strained ties between South Korea and Japan, which had long been tense due to disputes over wartime labor and other issues.

South Korean First Vice Foreign Minister Kim Hong Kyun met with Japanese Ambassador to Seoul Koichi Mizushima on Saturday to talk about the current political situation including the passage of the impeachment motion.

Kim emphasized that the government's foreign policy framework will remain consistent, and that it will continue to put effort into the development of South Korea-Japan relations, according to the South Korean Foreign Ministry.