At least one ballistic missile was reportedly fired by North Korea on Friday in a further sign of defiance by its leader Kim Jong Un in the face of tough new UN and US sanctions.
Military officials in the south signalled a missile flying some 800 kilometres before hitting the sea.
This could make it the isolated North’s first test of a medium range missile, capable of reaching Japan, since 2014.
The missile was launched from north of the capital, Pyongyang, flying across the peninsula and into the sea off the east coast early on Friday morning, the South’s Office of the Joint Chiefs of Staff said in a statement.
It appeared the North may have fired a second missile soon afterwards from the same region, with a projectile disappearing from radar at an altitude of about 17 km, it added.
It comes amid heightened tension on the Korean peninsula after the North rejected UN Security Council sanctions imposed earlier in the month in response to a nuclear test conducted in January and the United States issued fresh sanctions this week.
The US State Department said in a statement that it was closely monitoring the situation and urged North Korea to focus on taking concrete steps toward fulfilling its international commitments and obligations.
Japan quickly condemned the launch, lodging a protest with North Korea through its embassy in Beijing.
Prime Minister Shinzo Abe told parliament.
“Japan strongly demands North Korea to exercise self-restraint and will take all necessary measures, such as warning and surveillance activity, to be able to respond to any situations.”
Last week, the North fired two short-range missiles into the sea off its east coast and its leader Kim Jong Un ordered more nuclear weapons tests and missile tests to improve attack capability.