North Korea fires two missiles into the sea, its fifth such launch in recent weeks.
According to South Korea's military, the missiles are thought to be short-range ballistic missiles.
If confirmed, such a test would be a breach of 11 UN Security Council resolutions.
The launches come after US President Donald Trump said he had received a "very beautiful letter" from North Korean leader Kim Jong-un.
Trump said Kim was unhappy with the current US-South Korea joint military exercises.