The zone extends up to 200 nautical miles from Japan's coast, beyond the limits of its territorial waters.

"Two ballistic missiles fell inside the EEZ," said Kimi Onoda, parliamentary vice-minister of defence.

Prime Minister Fumio Kishida said there were no reports of damage, after South Korea's military announced the latest in a string of banned weapons tests by Pyongyang.

"Today's launches violate relevant UN Security Council resolutions and are a reckless act which escalates provocations against the international community," Kishida told reporters.

Japan has "lodged a firm protest against North Korea", he added.

Two weeks ago, Japan briefly activated its missile alert warning system for the southern Okinawa region when Pyongyang made what it called a failed attempt to put a satellite in space.

North Korean state media said the satellite had crashed into the sea soon after launch, as an "accident occurred" during its flight.