President Donald Trump on Monday affirmed Washington's "ironclad commitment" to Japan and South Korea  following the latest missile test by North Korea, the White House said.

The president spoke separately with Prime Minister Shinzo Abe of Japan and Acting President Hwang Kyo-Ahn of South Korea following Pyongyang's launch of four missiles that it said was part of training for a strike on US bases in Japan. 

Three of the missiles came down provocatively close to Japan.

"President Trump emphasized the United States' ironclad commitment to stand with Japan and South Korea in the face of the serious threat posed by North Korea," the White House statement said.

"He emphasized that his Administration is taking steps to further enhance our ability to deter and defend against North Korea's ballistic missiles using the full range of United States military capabilities."