North Korea tested the patience of its regional neighbors early Tuesday morning by firing a ballistic missile over Japan for the first time.
The projectile flew around 2,700 kilometers (1,678 miles) and "passed through the sky over Japan, according to a statement from South Korea’s Joint Chiefs of Staff carried by local news agency Yonhap. Yonhap later said the missile landed in the East Sea.
Seoul's presidential office also quickly called a meeting of the country's National Security Council.
Just a day earlier, South Korean President Moon Jae-in had ordered that his country be ready to quickly attack if North Korea "crosses the line."
Moon previously said his "red line" meant the North’s weaponizing of a nuclear-tipped intercontinental ballistic missile amid Pyongyang’s threats of opening fire towards Guam.
That marked a shift from his calls for peaceful dialogue since taking office in May.
North Korea has rejected Moon's stance as "insincere," instead conducting a series of missile tests, including a flurry of short-range projectiles Saturday morning.
The North's official Rodong Sinmun newspaper warned Monday that North Korean forces "will bury the entirety of the U.S. under water if the U.S. brings in the cloud of war of aggression on this soil."
Japan's Chief Cabinet Secretary Yoshihide Suga responded to Tuesday's provocation by condemning it as an "unprecedented grave threat."