North Korea launches ballistic test missile from submarine

North Korea fired a submarine-launched ballistic missile off its east coast, South Korea's military said on Wednesday, the latest in a string of missile launches by the isolated country in defiance of UN Security Council resolutions.

The missile was fired at around 5:30 a.m. from near the coastal city of Sinpo, where satellite imagery shows a submarine base to be located, and travelled about 500 kilometres, officials at South Korea's Joint Chiefs of Staff and the Defence Ministry told Reuters.

The projectile landed in Japan's air defence identification zone (ADIZ), an area of control designated by countries to help maintain air security, South Korea's Yonhap News Agency reported.

North Korea's "SLBM [submarine-launched ballistic missile] technology appears to have progressed," a South Korean military official told Reuters.

The United States detected and tracked the missile, which flew 480 km before splashing into the Sea of Japan, a U.S. defence official said on Tuesday.

"This was likely a KN-11 ballistic missile," the official said, speaking on condition of anonymity.

'Grave threat to Japan's security'

The launch came on the same day that the foreign ministers of China, Japan and South Korea were scheduled to meet in Tokyo.

"This poses a grave threat to Japan's security, and is an unforgivable act that damages regional peace and stability markedly," Japanese Prime Minister Shinzo Abe told reporters, adding that Japan had lodged a stern protest.

The launch also occurs two days after rival South Korea and the United States began annual military exercises in the South that North Korea condemns as a preparation for invasion, and has threatened retaliation.

South Korea's presidential office had said it planned to hold a national security council meeting at 7:30 a.m. Seoul time to discuss the missile test.

North Korea has become further isolated after a January nuclear test, its fourth, and the launch of a long-range rocket in February brought tightened UN sanctions.

It has launched numerous missiles of various types this year, including one this month that landed in or near Japanese-controlled waters.

Tensions on the Korean peninsula were exacerbated by the recent defection of North Korea's deputy ambassador in London to South Korea, an embarrassing setback to the regime of North Korean leader Kim Jong-un.

The North's missile tests this year include a launch from a submarine last month that appeared to have failed, according to South Korea's military. The July launch came a day after South Korea and the United States announced plans for the South to host a sophisticated U.S. anti-missile system.