The missiles were fired earlier this month (Picture: KCTV).
A series of short-range missile tests by North Korea earlier this month violated UN Security Council resolutions, a US national security adviser has said.
John Bolton said "there is no doubt" that the short-range ballistic missiles fired on 4 and 9 May had violated the resolutions.
Mr Bolton said the US is still willing to resume denuclearisation talks with North Korea but said the North's repeated failures to get rid of its weapons should be stopped.
His comments came a day after North Korea's official media said negotiations with Washington would not resume unless the US abandons what Pyongyang describes as unilateral disarmament demands.
North Korea has also strongly protested against the recent US seizure of a North Korean cargo ship that was involved in banned coal exports and demanded its immediate return.
Washington says the talks broke down because North Korea demanded sanctions relief in exchange for partially surrendering its nuclear capabilities.
Mr Bolton acknowledged the US has not been "hearing much from North Korea" since the Hanoi summit in February.
President Donald Trump, who is on a four-day visit to Japan, is set to discuss North Korea's missile and nuclear threats with Prime Minister Shinzo Abe.
The two leaders are also expected to discuss trade, security and tensions with Iran.