Millions of people in Japan woke up to a text message that said: "missile passing, please take cover."
Some of the country's famed high-speed trains came to a screeching halt early Tuesday morning after North Korea fired a missile over the island nation.
In the past, Pyongyang normally made a point of warning Japan before it launched a missile through its airspace, but not this time.
The missile was launched from near the capital city of North Korea, possibly from a mobile launch pad at Pyongyang airport. It flew more than 1,600 miles, crossing over the Japanese island of Hokkaido before splashing down in the Pacific Ocean.
Japanese Prime Minister Shinzo Abe called the launch "a reckless act," and an "unprecedented" threat.
South Korea, another U.S. ally, responded by releasing video of its own missile tests conducted last week. The U.S. and South Korea are currently holding joint military exercises which the North views as a rehearsal for war.
North Korea's missile launch is the latest show of force from leader Kim Jong Un, who has now fired 16 missiles so far this year.
The country also successfully tested two intercontinental ballistic missiles (ICBMs) last month capable of reaching the United States.
The U.S. and Japan have called for an emergency meeting of the United Nations Security Council later Tuesday to discuss the latest launch.
China, which has come under intense pressure from the Trump administration to pressure trading partner North Korea to halt missile tests, warned Tuesday that the standoff with the Kim regime had reached a "tipping point."