South Korea's Joint Chiefs of Staff (JCS) said that North Korea fired two short-range ballistic missiles toward the East Sea on Sunday.

The JCS said that it detected the missiles from the Munchon area in Gangwon Province between 1:48 a.m. and 1:58 a.m.

The JCS said that the missiles traveled about 350 kilometers at top speeds of Mach Five with an altitude of some 90 kilometers.

The intelligence authorities of South Korea and the United States are conducting a detailed analysis of the launch.

JCS Chairman Kim Seung-kyum had discussions with the United States right after the launch. The military said it will maintain a firm readiness posture while tracking and monitoring related movements in close cooperation with the United States in preparation against additional provocation.

The latest missile launch comes hours after South Korea and the United States wrapped up a joint naval exercise involving the USS Ronald Reagan aircraft carrier.

Sunday's launch, the seventh round of ballistic missile tests in two weeks, came on the eve of the 77th foundation anniversary of the North Korean ruling Workers’ Party. 

North Korea has conducted a number of missile launches in recent months, but it is the first time this year that the North conducted a nighttime launch.  

Pyongyang has conducted 23 ballistic missile and two cruise missile tests so far this year.