North Korea has test-fired what appeared to be a submarine-launched ballistic missile off its east coast, the US and South Korea said.
The missile was fired from a location near the North Korean coastal town of Sinpo, where analysts have previously detected efforts by the North to develop submarine-launched ballistic missile systems, said an official from Seoul's defence ministry. The official could not confirm how far the missile travelled or where it landed.
South Korea's Joint Chiefs of Staff said in a statement that it presumed the missile successfully ejected from the submarine's launch tube but failed in its early stage of flight.
South Korea's Yonhap news agency said the missile probably flew only a few miles before exploding in mid-air, but the defence ministry official could not confirm the report.
The US Strategic Command also said that the missile was tracked over the sea between the Korean Peninsula and Japan, where it apparently fell.
"We strongly condemn this and North Korea's other recent missile tests, which violate UN Security Council resolutions explicitly prohibiting North Korea's launches using ballistic missile technology," said Commander Gary Ross, a Pentagon spokesman.
North Korea acquiring the ability to launch missiles from submarines would be an alarming development for rivals and neighbours because missiles from submerged vessels are harder to detect in advance.
While security experts say it is unlikely that North Korea possesses an operational submarine capable of firing missiles, they acknowledge that the North is making progress on such technology.
North Korea already has a considerable arsenal of land-based ballistic missiles and is believed to be advancing its efforts to miniaturise nuclear warheads mounted on missiles through nuclear and rocket tests.
North Korea last test-fired a submarine-launched ballistic missile in April, calling it a success that strengthened its ability to attack enemies with "dagger of destruction". South Korean defence officials said then that the missile flew about 30 kilometres (19 miles) before probably exploding in mid-air.
The North also test-fired a submarine-launched ballistic missile on December 25, but that test was seen as a failure, the South's Joint Chiefs of Staff said. The North first claimed a successful submarine-launched missile test in May last year.
Saturday's launch came a day after US and South Korean military officials said they were ready to deploy an advanced US missile defence system in South Korea to cope with North Korean threats.
Seoul and Washington launched formal talks on deploying the Terminal High-Altitude Area Defence, or THAAD, after North Korea conducted a nuclear test and a long-range rocket launch earlier this year. China, Russia and North Korea all say the THAAD deployment could help US radars spot missiles in their countries.
The deployment decision for THAAD was announced hours after North Korea angrily reacted to new US sanctions on leader Kim Jong Un and other top officials for human rights abuses, with Pyongyang's foreign ministry saying such measures were tantamount to declaring war.
North Korea has already been sanctioned heavily because of its nuclear weapons programme. However, the action by the Obama administration on Wednesday marked the first time Kim has been personally targeted, and also the first time that any North Korean official has been blacklisted by the US treasury in connection with reports of rights abuses.
The US stations about 28,500 troops in South Korea as deterrent against potential aggression from North Korea.