North Korea fired a submarine-launched ballistic missile off its east coast early on Wednesday, South Korea's military said, 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. (2030 GMT) from near the coastal city of Sinpo, where satellite imagery shows a submarine base to be located, and travelled about 500 kilometres (311 miles), 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 launch comes 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 which 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.