North Korea has test-fired two mid-range ballistic missiles from its eastern coast, says South Korea.
The first launch was considered to have failed, travelling about 150km (90 miles) before landing in the sea.
The second, launched hours later, flew about 400km. Military officials in the South said both were intermediate-range Musudan missiles.
A confirmed successful test would mark a step forward for North Korea after four failed launches in recent months.
South Korea’s Joint Chiefs of Staff said Seoul and the US were “carrying out an in-depth analysis” of the second launch, and did not say whether it was considered a success.
North Korea, which is developing nuclear weapons, is banned by UN resolutions from any use of ballistic missile technology.
South Korea’s presidential office announced that it would hold a national security meeting to discuss the launch.
“We intend to raise our concerns at the UN to bolster international resolve in holding [North Korea] accountable for these provocative actions,” said Kirby in a statement.
North American Defense Command (Norad), which tracked the missiles, determined they did not pose a threat to North American territories.
Japanese Prime Minister Shinzo Abe has said such tests “clearly cannot be tolerated”.
The Musudan is believed to have a range of about 3,000km (1,800 miles), enough for it to hit South Korea, Japan and the US territory of Guam in the Western Pacific.
North Korea is thought to have dozens of them but has never successfully tested one.
The four other missiles tested in the last two months either exploded mid-air or crashed.
The BBC’s Steve Evans in Seoul says the repeated the failures illustrate both the technological difficulties North Korea faces as it develops deliverable nuclear weapons, and its determination to succeed.
Surrounding countries had detected preparations for a launch in the past few days and warned that it was about to happen.