North Korea fired what is thought to be an intercontinental ballistic missile (ICBM) towards the sea off its east coast on Thursday, militaries in South Korea and Japan said, in what would be the first full-capability launch of the nuclear-armed state’s largest missiles since 2017.

South Korea’s Joint Chiefs of Staff said it had detected the launch of an “unidentified projectile” from North Korea. It said the launch was assumed to be a long-range missile, possibly an intercontinental ballistic missile (ICBM) fired on a “lofted” trajectory high into space, Yonhap news agency reported.

South Korea’s ministry of defence did not immediately confirm whether the test involved an ICBM. North Korea has not tested such missiles at full range or capability since 2017.

Japan’s coast guard said the projectile landed inside Japan’s exclusive economic zone (EEZ), 170km west of Aomori Prefecture in northern Japan, at 0644 GMT.

On March 16, North Korea launched a suspected missile that appeared to explode shortly after liftoff over Pyongyang, South Korea’s military said, amid reports that the nuclear-armed North was seeking to test-fire its largest missile yet.

The US and South Korea have warned in recent weeks that North Korea may be preparing to test-fire an ICBM at full range for the first time since 2017. US officials said that at least two recent tests, on February 27 and March 5, featured North Korea’s largest ICBM system yet.