The United States called on North Korea Monday to "cease its unlawful and destabilizing activities," after Pyongyang fired two suspected ballistic missiles in its fourth weapons test this month, a State Department spokesman said.

In a call with South Korean and Japanese officials, the US special representative on North Korea, Sung Kim "expressed concern" about the missile launches and urged Pyongyang to return to dialogue "without preconditions," the statement from spokesman Ned Price said, AFP reports.

He also "reaffirmed the US commitment to the complete denuclearization of the Korean Peninsula, as well as its ironclad commitment to the defense of its allies," South Korea and Japan.

Two suspected "short-range ballistic missiles" were fired east from an airport in Pyongyang early Monday, the South Korean military's Joint Chiefs of Staff said, with Japan also confirming the launch.