North Korea has fired a ballistic missile over Japan, with the projectile falling into waters off the country's eastern coast.
The Japanese government's warning system urged people in an area in the north of the country to take precautions early on Tuesday morning.
South Korea's military said the missile travelled 1,678 miles and was fired from North Korea's Sunan region, near the capital Pyongyang, just before 6.00am local time.
But Japan's military did not attempt to shoot down the missile, which broke into three pieces and fell into the sea east of Hokkaido.
There was no damage reported and the Pentagon said the missile posed no threat to US territory.
Earlier in August, North Korean leader Kim Jong Un had threatened to fire missiles at the US Pacific territory of Guam.
US President Donald Trump had promised "fire and fury" for North Korea if it threatened the US.
Tensions appeared to have eased in recent weeks, although North Korea has previously reacted angrily to US/South Korean military drills, such as the ones currently underway, which it describes as an invasion rehearsal.
Today, President Trump insisted that "all options are on the table" following the latest launch.
In a statement, the US president said: "The world has received North Korea's latest message loud and clear: this regime has signalled its contempt for it neighbours, for all members of the United Nations, and for minimum standards of acceptable international behaviour.
"Threatening and destablising actions only increase the North Korea regime's isolation in the region and among all nations of the world. All options are on the table."
Following Tuesday's missile launch, Japan's Prime Minister Shinzo Abe said his country's authorities would "gather information and analyse" the situation, adding: "We'll take all possible measures to ensure people's safety".
"We will do our utmost to protect people's lives," he added.
"This reckless act of launching a missile that flies over our country is an unprecedented, serious and important threat."
Mr Abe told reporters that he had spoken with Donald Trump by phone following the launch.
US Secretary of State Rex Tillerson and South Korea's foreign minister agreed to consider tougher sanctions against North Korea following the missile launch.