Tensions on the Korean Peninsula have eased after the historic summit between U.S. and North Korean leaders, Japan's top government spokesman said Wednesday.

"It is clear that, through this summit, the severe security conditions that meant we were always on alert for incoming missiles (from North Korea) were alleviated," Chief Cabinet Secretary Yoshihide Suga told a press conference.

In the first-ever U.S.-North Korean summit in Singapore on Tuesday, North Korean leader Kim Jong Un pledged to work toward the "complete" denuclearization of the Korean Peninsula, while U.S. President Donald Trump committed to provide security guarantees to Pyongyang.

In marked contrast to the recent conciliatory mood, North Korea last year carried out a nuclear test and launched two ballistic missiles over Japan.

The government spokesman also said that Japan will offer to assist in the denuclearization process in cooperation with the United States and South Korea.

(People walk past a large screen in Tokyo broadcasting the U.S.-North Korea summit)

Noting that "a step toward various issues concerning North Korea" has been initiated by the U.S.-North Korea summit, Suga welcomed Trump raising the issue of Japanese nationals abducted by the North decades ago, something Prime Minister Shinzo Abe's government views as its top priority.

Although a joint statement released after the summit did not specify a time frame to achieve denuclearization, Suga said, "The North Korean issues are not easy ones that could be settled in a summit."