North Korea has fired another ballistic missile, the latest in a series of launches that have raised tensions with its neighbours and the US.
The Pentagon said it believed it was an intercontinental ballistic missile that flew for about 1,000km (620 miles) and fell into the Sea of Japan.
South Korean news agency Yonhap said that the missile was launched from Pyongsong, South Pyongan province.
North Korea's last ballistic missile test was in September.
That came days after it had conducted its sixth - and largest - nuclear test.
The US said the latest launch happened at about 03:30 local time (18:30 GMT).
US President Donald Trump was briefed while the missile was still in the air, the White House has said. He was visiting Congress at the time, but has since returned to the White House.
South Korea's military said it had responded to the launch with a missile exercise of its own.
The North is thought to be focusing efforts on building long-range missiles with the potential of reaching the mainland continental US.
Pyongyang officials said the first of the longer-range missiles it tested in July could hit "any part of the world", but the US military called it an intermediate-range missile instead.
Its last nuclear test reportedly involved a miniaturised hydrogen bomb that could be loaded on to a long-range missile, raising tensions with the US even further.
Last week, the US imposed fresh sanctions against North Korea over its nuclear programme. The measures targeted North Korean shipping operations and Chinese companies that traded with Pyongyang.