North Korea has fired a ballistic missile, US and South Korean officials have confirmed.
The missile flew to the east and landed in the sea near Japan, analysts said. US officials confirmed the launch to Reuters, while South Korea's Joint Chiefs of Staff also confirmed details to the news agency Yonhap.
The Pentagon said it had detected a "probable" missile. Spokesman Colonel Rob Manning added: "We are in the process of assessing the situation and will provide additional details when available."
The South's unification minister added that signs of unusual activity had been detected in North Korea. Japan ordered an emergency meeting of cabinet ministers, the government's chief cabinet secretary said.
Minutes after the North fired the missile, South Korea's military conducted a missile-firing test in response to the provocation, the South Korean military said.
Two US government sources said earlier that US government experts believed North Korea could conduct a new missile test within days, in what would be its first launch since it fired a missile over Japan in mid-September.
North Korea has this year escalated its nuclear weapons programme, launching a series of hydrogen bomb and missile tests, leading analysts to conclude the rogue state could soon be in striking distance of the US mainland.
Reports of the launch came after the US announced it would begin testing its nuclear warning siren system in Hawaii for the first time since the Cold War.
More to follow.