SEOUL/TOKYO (Reuters) -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 wailed across the South Korean capital of Seoul around 6:32 a.m. (2132 GMT Tuesday) 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 morning, saying a missile had been launched from North Korea.

North Korea has said it will launch its first military reconnaissance satellite between May 31 and June 11 to boost monitoring of U.S. activities.

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.

(Reporting by Hyonhee Shin; Editing by Chris Reese and Sonali Paul)