The flying objects are believed to have been launched from the port city of Wonsan at around 8:10 a.m. local time on May 8, Reuters reported.
South Korea is actively exchanging information with Japan to assess the situation and share data related to the launch.
Pyongyang has continued to promote missile development activities in recent years, including missiles with different ranges.
In early May, North Korean leader Kim Jong-un visited a tank factory and praised the country's tank manufacturing technology. The visit comes as North Korea is stepping up efforts to upgrade conventional troops, in parallel with developing a nuclear and missile arsenal.
Previously, Mr. Kim Jong-un also attended the launching ceremony of a new ship area and supervised tests related to drones and many other weapons.
The latest launch comes amid rising military tensions between the two Koreas. Previously, in March, North Korea also launched many ballistic missiles and condemned joint exercises between the South Korean military and its allies as a provincial and dangerous act.
