"Our military detected two ballistic missiles North Korea fired from areas near Pyongyang into the East Sea at 11.55 p.m. on Monday and at midnight of Tuesday," it said.

Both missiles flew about 400 km before falling into the sea, Yonhap News Agency quoted the JCS as saying.

The military is still analysing the North's latest missile launch to determine the exact type of the missiles fired, according to the JCS.

The North's latest missile launch comes as a nuclear-powered American submarine, USS Annapolis, arrived at a naval base in South Korea's southern island of Jeju as part of efforts to bolster joint deterrence against North Korea's evolving threats.

North Korea fired two ballistic missiles into the East Sea on July 1, followed by multiple cruise missile launches on July 22.