North Korea has fired at least one ballistic missile, which flew about 800km before hitting the sea off its east coast, South Korea's military says, as the isolated state stepped up its defiance of tough new UN and US sanctions.
South Korea's Yonhap news agency said the missile was likely a medium-range Rodong-missile. If confirmed, it would mark North Korea's first test of a medium-range missile, capable of reaching Japan, since 2014.
The launch 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 US issued fresh sanctions this week.
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 after from the same region, with a projectile disappearing from radar at an altitude of about 17km, it added.
South Korea did not confirm the type of the missiles, but 800km was likely beyond the range of most short-range missiles in the North's arsenal.
The North's Rodong missile has an estimated maximum range of 1300 km, according to the South's defence ministry.
A US official told Reuters that it appeared to be a medium-range missile fired from a road-mobile launcher.
The US State Department said in a statement it was closely monitoring the situation and urged North Korea to focus on taking 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," Abe said.
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.
New US sanctions on Pyongyang were issued on Wednesday aiming to expand its blockade by blacklisting individuals and entities that deal with the North's economy.
The North has also reacted angrily to annual joint military drills by US and South Korean troops that began on March 7, calling the exercises "nuclear war moves" and threatening to wipe out its enemies.