North Korea launched what it called a space satellite toward the south on Wednesday, South Korea's military said, prompting emergency alerts and evacuation warnings in parts of South Korea and Japan.
Air raid sirens were heard across Seoul around 6.32am local time (7.32 AEST) as the city issued a warning asking citizens to prepare for potential evacuation.
The Japanese government issued an emergency warning over its J-Alert broadcasting system for residents of the southern prefecture of Okinawa early on Wednesday, saying a missile had been launched from North Korea.
In data provided to international authorities, North Korea said the launch would carry the rocket south, with various stages and other debris expected to fall over the Yellow Sea and into the Pacific Ocean.
North Korea previously said it will launch its first military reconnaissance satellite between May 31 and June 11 to boost monitoring of US activities.
Analysts say the satellite will improve North Korea's surveillance capability, enabling it to strike targets more accurately in the event of war.