North Korea fired multiple ballistic missiles, one of which was a possible intercontinental ballistic missile (ICBM).

This caused an alert for residents in parts of central and northern Japan to seek shelter. Officials in South Korea and Japan said the missile may have been an ICBM, which are North Korea’s longest-range weapons. Here’s what we know so far.

What We Know About the Missile Launch

The missile was launched at around 5:30 a.m. from Sunan International Airport near Pyongyang, North Korea’s capital city. Japanese officials said the missile appeared to break into three pieces and land in waters off Japan’s coast. It was not immediately clear if the missile was armed with a nuclear warhead.

South Korean military analysts are saying that Thursday’s launch may have been a “new type” of ICBM. The analysts said the missile reached a maximum height of about 4,475 miles, which is significantly higher than any other missiles North Korea has previously tested.

Why This Matters

This latest launch comes just days after North Korea conducted its sixth nuclear test, which it claims was a hydrogen bomb that can be fitted onto an ICBM. Analysts believe North Korea is now close to its goal of developing a nuclear weapon that can target the United States mainland. In response to the nuclear test, the U.N. Security Council voted unanimously to impose new sanctions on North Korea.

In addition to yesterday’s launch, North Korea has also conducted a series of shorter-range missile tests in recent months. These tests have caused alarm in neighboring countries like Japan and South Korea because they show that North Korea’s missiles are becoming increasingly sophisticated and could soon pose a direct threat to those countries.