North Korea has fired a missile eastwards from its capital, Pyongyang, towards Japan, the South Korean and Japanese governments say.
The missile is likely to have reached an altitude of about 770km (478 miles) and travelled some 3,700km, South Korea’s military said.
South Korea and the US are analysing the details of the launch, it added.
Last month, North Korea fired a missile over Japan in what Tokyo called an “unprecedented threat”to the country.
The missile launch comes just days after new sanctions were imposed on North Korea by the United Nations because of its weapons testing.
In response to the missile alert on Friday, South Korea’s military conducted a ballistic missile drill in the Japan Sea, known as the East Sea, Yonhap news agency reports.
South Korea’s presidential palace, the Blue House, has called an urgent National Security Council meeting.
Late last month, North Korea fired a domestically made Hwasong-12 missile over Japan it what Pyongyang said was “the first step” of military operations in the Pacific.
The Hwasong-12 crossed Japan’s northern Hokkaido island, triggering public alerts to take cover, before landing in the sea.
The UN Security Council has repeatedly condemned North Korea for its actions.