U.S. national security adviser John Bolton said on Saturday that North Korea's recent missile launches violated a U.N. Security Council resolution and urged leader Kim Jong Un to return to denuclearization talks.

It was the first time a senior U.S. official has described the tests as a violation of U.N. resolutions aimed at halting North Korea's nuclear and missile programs and came ahead of a four-day visit to Japan by U.S. President Donald Trump who was to arrive later in the day.

"The U.N. resolution prohibits the launch of any ballistic missiles," Bolton said at a press roundtable. North Korea's test firings included short range ballistic missiles and so there was "no doubt" it was a violation, he added.