The one-line announcement from the South's Joint Chiefs of Staff did not immediately provide further details and came shortly after 3:00 am (0800 GMT) in Washington, DC on one of the US' biggest annual holidays.

Thursday's launch was the latest in a series of weapons tests by Pyongyang, which fired what it called two "super-large multiple rocket launcher" systems last month.

Japan's Jiji Press quoted sources from the defence ministry in Tokyo saying two projectiles were launched from the North's east coast, adding they appeared to be ballistic missiles -- which Pyongyang is banned from firing under UN Security Council resolutions.

US President Donald Trump has played down the recent launches, repeatedly pointing to North Korea's moratorium on nuclear tests and intercontinental ballistic missile launches as foreign policy successes for him.

But negotiations between Pyongyang and Washington have been gridlocked since a second summit between Trump and North Korean leader Kim Jong Un in Hanoi in February collapsed without a deal.

North Korea is under multiple sets of international sanctions over its nuclear weapon and ballistic missile programmes and lifting some of them was a key demand at the Hanoi summit.

Earlier this month, Seoul and Washington said they would postpone planned joint military exercises to ease diplomacy with the North, an announcement Pyongyang dismissed.

North Korea has issued a series of increasingly assertive comments in recent weeks as its end-of-year deadline for the US to come up with a fresh offer approaches.

Trump hinted at the prospect of a fourth meeting with Kim in a tweet earlier this month, only to be rebuffed by the North, which said it had no interest in summits "that bring nothing to us".