North Korea has fired a ballistic missile, South Korea's military says, in the first such test since Donald Trump took office as US president.
The missile was launched at 07:55 local time (22:55 GMT on Saturday) and flew east towards the Sea of Japan for about 500km, South Korean officials say.
Pyongyang has conducted a number of nuclear tests in the past year.
North Korea's repeated missile and nuclear tests and aggressive statements continue to alarm and anger the region.
Sunday's launch took place from the Banghyon air base in North Pyongan province on the west side of the Korean peninsula.
A US defence official quoted by Reuters news agency said Washington "can confirm that we did detect a missile launch from North Korea".
A White House official said that President Trump had been briefed on the launch.
South Korea's foreign ministry said that "North Korea's repeated provocations show the Kim Jong-un regime's nature of irrationality, maniacally obsessed in its nuclear and missile development".
Japan's Chief Cabinet Secretary Yoshihide Suga said the missile had not reached Japanese territorial waters, adding that Tokyo would make a "strong protest" to North Korea over the incident.
There has so far been no comment from North Korea,
North Korean leader Kim Jong-un said in January that the country was close to testing long-range missiles capable of carrying nuclear warheads.
On a visit to South Korea last week, US Defence Secretary James Mattis said that any use of nuclear weapons by North Korea would be met with an "effective and overwhelming" response.
He also reconfirmed plans to deploy a US missile defence system in South Korea later this year.
North Korea conducted its fifth test of a nuclear device last year, and claims it is capable of carrying out a nuclear attack on the US, though experts are still unconvinced that its technology has progressed that far.
It has also said in recent weeks that it has a new intercontinental ballistic missile, capable of reaching the US mainland, which it is prepared to test launch at any time.