North Korea on Tuesday fired a ballistic missile over Japan for the first time in five years, forcing Japan to issue evacuation notices and suspend trains during the flight of the nuclear-capable weapon that could reach the U.S. territory of Guam and possibly beyond.

The launch was the most provocative weapons demonstration by North Korea this year as it ramps up missile tests to build a full-fledged nuclear arsenal that viably threatens U.S. allies and the American homeland with the goal of wresting outside concessions, some experts say.

The missile’s estimated 4,500 kilometer (2,800 mile) flight was the longest by any North Korean missile, though the North has previously launched other potentially longer-range weapons at high angles to avoid neighboring countries.

The United States strongly condemned North Korea’s “dangerous and reckless decision” to launch what it described as a “long-range ballistic missile” over Japan.

“The United States will continue its efforts to limit (North Korea’s) ability to advance its prohibited ballistic missile and weapons of mass destruction programs, including with allies and U.N. partners,” National Security Council spokesperson Adrienne Watson said in a statement.

South Korean President Yoon Suk Yeol earlier said the missile had an intermediate range, while Japanese Defense Minister Yasukazu Hamada said it was believed to have an intermediate range or longer. If Tuesday’s launch involves a long-range missile, that could be a test of a weapon targeting the U.S. homeland, some experts say.

Japanese authorities alerted residents in northeastern regions to evacuate to shelters, in the first “J-alert” since 2017 when North Korea fired an intermediate-range Hwasong-12 missile twice over Japan in a span of weeks during its previous torrid run of weapons tests.

Trains were suspended in the Hokkaido and Aomori regions until the government issued a subsequent notice that the North Korean missile appeared to have landed in the Pacific. In Sapporo city, the prefectural capital of Japan’s northernmost main island of Hokkaido, subways were also temporarily suspended, with stations packed with morning commuters.

Japanese Prime Minister Fumio Kishida told reporters the latest firing “is a reckless act and I strongly condemn it.”

South Korea’s Joint Chiefs of Staff said the missile was fired from the inland north in North Korea. It warned the North’s repeated missile launches would only deepen its international isolation and prompt Seoul and Washington to bolster their deterrence capacities.

Yoon said the North’s “reckless nuclear provocations” would meet the stern response of the South and the broader international community.

According to South Korean and Japanese estimates, the missile traveled about 4,500-4,600 kilometers (2,800-2,860 miles) at a maximum altitude of 970-1,000 kilometers (600-620 miles). Hamada said it landed in the Pacific, about 3,200 kilometers (1,990 miles) off the northern Japanese coast and that there have been no reports of damage to Japanese aircraft and ships.

South Korea’s Defense Ministry said the missile flew farther than any other weapon fired by North Korea. Before Tuesday’s launch, the 3,700-kilometer (2,300 miles)-long flight of Hwasong-12 in 2017 was North Korea's longest. It has previously tested intercontinental ballistic missiles at steep angles so they flew shorter.

The U.S. said national security adviser Jake Sullivan had consulted with his South Korean and Japanese counterparts on their appropriate and robust responses. Both South Korea and Japan separately convened their own emergency national security council meetings.

The missile’s flight distance shows it has enough range to hit the U.S. Pacific territory of Guam, home to U.S. military bases that sent advanced warplanes to the Korean Peninsula in shows of force in past tensions with North Korea. In 2017, North Korea threatened to make “an enveloping fire” near Guam with Hwasong-12 missiles amid rising animosities with the then-Trump administration.

North Korea last test-fired a Hwasong-12 missile in January. At the time, the North said the launch was meant to verify the overall accuracy of the weapon, which it said was launched on a lofted angle to prevent it from flying over other countries.

Hamada said the missile on Tuesday could have been another Hwasong-12.

Kim Dong-yub, a professor at Seoul’s University of North Korean Studies, said North Korea could have tested the Hwasong-12 again or even an intercontinental ballistic missile, closer to what would be a normal ballistic trajectory but shorter than its full range. If it was an ICBM, the purpose of the launch would be to test whether the warhead could survive the harsh conditions of atmospheric reentry, Kim said.

Tuesday’s launch is the fifth round of weapons tests by North Korea in the past 10 days in what was seen as an apparent response to military drills between South Korea and the United States and other training among the allies including Japan last week. North Korea views them as an invasion rehearsal.

The missiles fired during the past four rounds of launches were short-range and fell in the waters between the Korean Peninsula and Japan. Those missiles are capable of hitting targets in South Korea.

North Korea has test-fired about 40 missiles over about 20 different launch events this year as its leader Kim Jong Un pushes to perfect his country's weapons technologies and refuses to return to nuclear diplomacy with the United States.

Last month, North Korea adopted a new law authorizing the preemptive use of nuclear weapons in some cases, a move that showed its increasingly aggressive nuclear doctrine. Last Saturday, Yoon warned of an “overwhelming response” from South Korean and U.S. militaries if North Korea uses nuclear weapons.

Some foreign experts say North Korea needs to master a few remaining technologies to acquire functioning nuclear missiles. Each new test pushes them closer to being able to reach the U.S. mainland and its allies with a host of nuclear-tipped missiles of varying range.

Some experts say Kim eventually will return to diplomacy and use his enlarged arsenal to pressure Washington to accept his country as a nuclear state, a recognition that he thinks is necessary to win the lifting of international sanctions and other concessions.