North Korea has fired a ballistic missile into the waters off its east coast, US and South Korean officials said, amid worries that Pyongyang might soon conduct banned nuclear or long-range rocket tests.
The firing was also made as North Korea expressed anger over annual military drills between the United States and South Korea that the North sees as an invasion rehearsal.
The US Pacific Command said it detected and tracked what it assessed as a North Korean missile launched from land near the eastern city of Sinpo.
A US statement said initial assessments indicate the type of missile was a KN-15 medium-range ballistic missile.
South Korea's Joint Chiefs of Staff issued a similar assessment, saying the missile flew about 37 miles - a much shorter distance than other North Korean missiles travelled in their recent test launches.
Two weeks ago the South Korean and US militaries said they had detected a failed North Korean ballistic missile launch.
South Korean media speculated at the time that North Korea might have attempted to test a missile that it has not deployed.
Earlier in March, North Korea fired four ballistic missiles that flew about 620 miles, with three of them landing in waters that Japan claims as its exclusive economic zone.
The North's latest launch came as outside satellite imagery show possible preparations for a new nuclear test at the North's main nuclear test site, such as communication cables used to initiate a test and collect data being already laid.
North Korea's state media has also said the world will soon witness what it calls "eventful successes" the country achieves in the space development.
Washington, Seoul and others call the North's space programme a cover for its long-range missile development scheme.
North Korea is pushing hard to upgrade its weapons systems to cope with what it calls US hostility.
Many weapons experts say the North could have a functioning nuclear-tipped missile capable of reaching the continental US within a few years. North Korea carried out two nuclear tests last year.
North Korea also often responds to US-South Korean military drills with its own military training and harsh rhetoric.
The allies say the drills set to run until the end of this month are defensive in nature.
US secretary of state Rex Tillerson said "the United States has spoken enough about North Korea" in reaction to the launch.
The State Department issued a terse statement from America's top diplomat acknowledging "yet another" launch and saying: "We have no further comment."
Ralph Cossa, president of the Pacific Forum CSIS think tank in Honolulu, said he was expecting North Korea would do something to coincide with the Trump-Xi summit, perhaps conducting a nuclear test.
He said the missile launch may be a precursor, with more to come as the summit starts later this week.
"I've joked before that they don't mind being hated but they definitely hate to be ignored," he said.
South Korea's Foreign Ministry called the North's latest missile launch a "reckless provocation" that posed a threat to international peace, while Japan's chief cabinet secretary Yoshihide Suga said the country lodged a strong protest.