SEOUL, South Korea (AP) -- Alarms blared from cellphones, radios and public loudspeakers and fishermen hurried back to shore in northern Japan on Thursday after North Korea fired an intercontinental ballistic missile above its eastern waters, adding to a recent barrage of provocative weapons demonstrations that officials say may culminate with a nuclear test in coming weeks.
The ICBM test, which was followed by two short-range ballistic launches into the sea, was swiftly condemned by North Korea's neighbors and the United States, which said it is willing to take "all necessary measures" to ensure the safety of the American homeland and allies South Korea and Japan.
The Biden administration also warned of unspecified "additional costs and consequences" if North Korea goes on to detonate a nuclear test device for the first time since September 2017.
The launches are the latest in a series of North Korean weapons tests in recent months that have raised tensions in the region. They came a day after the North fired more than 20 missiles, the most it has launched in a single day ever.
South Korea's Joint Chiefs of Staff said it detected that North Korea fired an ICBM from an area near its capital, Pyongyang, at about 7:40 a.m. and then two short-range missiles an hour later from the nearby city of Kaechon that flew toward its eastern waters.
The longer-range missile appeared to be fired at a high angle, possibly to avoid entering the territory of neighbors, reaching a maximum altitude of 1,920 kilometers (1,193 miles) and traveling around 760 kilometers (472 miles), according to South Korea's military.
It wasn't immediately clear whether the launch was successful.
Japan's military announced similar flight details. It also said it lost track of one of the North Korean weapons, apparently the ICBM, after it "disappeared" in skies above waters between the Korean Peninsula and Japan. South Korea said the short-range missiles traveled about 330 kilometers (91 miles), falling closer to North Korea's eastern coast.
Choi Yong Soo, a South Korean navy captain who handles public affairs for Seoul's Defense Ministry, didn't answer directly when asked about the possibility of the ICBM launch being a failure, saying that it is still being analyzed.
Citing anonymous military sources, South Korea's Yonhap news agency reported that the missile possibly failed to maintain a normal flight following a stage separation.
The Japanese government initially feared North Korea fired a missile over its northern territory but later adjusted its assessment. Japanese Chief Cabinet Secretary Hirokazu Matsuno said the alerts were based on a trajectory analysis that indicated a flyover.
The office of Japanese Prime Minister Fumio Kishida broadcast the "J-Alert" warnings through television, radio, mobile phones and public loudspeakers to residents of the northern prefectures of Miyagi, Yamagata and Niigata, instructing them to go inside strong buildings or underground.
There have been no reports of damage or injuries in the regions where the alerts were issued. Bullet train services in some areas were temporarily suspended following the missile alert before resuming shortly.
North Korean missile activity is a particular concern in Niigata, which is home to seven reactors at the Kashiwazaki-Kariwa nuclear power plant. Those reactors are currently offline and Japanese authorities say no abnormalities have been detected.
On Sado island, just off Niigata's northern coast, fishermen rushed back from sea at the sound of sirens blaring from community speaker systems. One fisherman told NTV television he no longer feels safe going out to sea.
"We really have to be careful," he said.
North Korea last flew a missile over Japan in October in what it described as a test of a new intermediate-range ballistic missile, which experts say potentially would be capable of reaching Guam, a major U.S. military hub in the Pacific.
Kishida condemned North Korea's latest launches and said officials were analyzing the details of the weapons. The office of South Korean President Yoon Suk Yeol said his national security director, Kim Sung-han, discussed the launches during an emergency security meeting at which members talked about plans to strength the country's defense in conjunction with its alliance with the United States.
The office said South Korea will continue combined military exercises with the United States in response to North Korea's intensified testing activity, which it said would only deepen the North's international isolation and unleash further economic shock to its people.
Adrienne Watson, a spokesperson for the U.S. National Security Council, issued a statement saying the United States strongly condemns North Korea's ICBM test and that President Joe Biden and his national security team are assessing the situation in close coordination with allies and partners.
"This launch, in addition to the launch of multiple other ballistic missiles this week, is a flagrant violation of multiple U.N. Security Council resolutions and needlessly raises tensions and risks destabilizing the security situation in the region," Watson said.
She said the United States will take all necessary measures to ensure the security of America and its allies South Korea and Japan.
One of the more than 20 missiles North Korea shot on Wednesday flew in the direction of a populated South Korean island and landed near the rivals' tense sea border, triggering air raid sirens and forcing residents on Ulleung island to evacuate. South Korea quickly responded by launching its own missiles in the same border area.
Those launches came hours after North Korea threatened to use nuclear weapons to get the U.S. and South Korea to "pay the most horrible price in history" in protest of ongoing South Korean-U.S. military drills that it views as a rehearsal for a potential invasion.
Following North Korea's additional launches on Thursday, the South Korean and U.S. air forces agreed to extend an ongoing combined aerial drill to step up their defense posture in the face of North Korea's increased weapons testing and growing nuclear threat.
U.S. and South Korean forces have deployed more than 200 warplanes, including advanced F-35 fighter jets, for the "Vigilant Storm" exercises that were initially scheduled through Friday. South Korea's air force didn't immediately say how long the training will continue, noting that the allies are still discussing details.
North Korea has been ramping up its weapons demonstrations to a record pace this year. It has fired dozens of missiles, including previous ICBM launches in March and May, as it exploits the distraction created by Russia's war in Ukraine and a pause in diplomacy to push forward arms development and dial up pressure on the United States and its Asian allies.
North Korea has punctuated its tests with an escalatory nuclear doctrine that authorizes preemptive nuclear attacks over a variety of loosely defined crisis situations. U.S. and South Korean officials say North Korea may up the ante in the coming weeks with a nuclear test, which would be its seventh overall.
Experts say such tests could bring North Korea a step closer to its goal of building a full-fledged arsenal threatening regional U.S. allies and the American mainland.
"Should it go forward with a seventh nuclear test there would be additional costs and consequences," State Department spokesperson Ned Price said Tuesday, noting that the test would be a "dangerous, reckless, destabilizing act."
Experts say North Korea is escalating a brinkmanship aimed at forcing the United States to accept it as a nuclear power and negotiating economic and security concessions from a position of strength. Nuclear disarmament talks between Washington and Pyongyang have been stalled since 2019 because of disagreements over an easing of crippling U.S.-led sanctions against North Korea in exchange for its denuclearization steps.