North Korea fired several ballistic missiles toward the sea off its east coast on Wednesday over a dispute.
The South Korean military said that an attack of ballistic missiles followed as Pyongyang doused Seoul's hopes of an easing in tensions.
The U.S. and South Korean authorities were conducting a detailed analysis of the launch.
South Korea's Joint Chiefs of Staff said the unidentified short-range missiles flew 240 km and were launched from the North's east coast.
The military officials also detected the launch of a suspected ballistic missile from near Pyongyang on Tuesday.
Meanwhile, South Korea's presidential Blue House convened an emergency National Security Council meeting on Wednesday.
The blue house called these missile launches a provocation that violated U.N. Security Council resolutions, urging Pyongyang to end such tests.
As Pyongyang's actions "threaten peace and security in the region and the international community, Tokyo would cooperate with Seoul and Washington to monitor the situation," said the Blue House.
The latest attack marks North Korea's fourth and fifth ballistic missile launches this year, following two launches in January and another in March.
Hostile Enemy:
The disclosure of the latest launches came after a combative statement by a top North Korean official that made clear that Pyongyang saw no shift in its hostile stance toward Seoul despite hopes of a thaw in relations.
The two nations remain technically at war after their 1950-1953 conflict ended in a truce.
Notably, the latest attacks fired by North Korea this week did not enter the country's territorial waters or exclusive economic zone and caused no damage.
