South Korea's Joint Chiefs of Staff (JCS) said it detected the launches from Chunghwa County, some 60 kilometers south of Pyongyang, from 8 a.m. and that the missiles traveled some 350 km before splashing into the sea, Yonhap news agency reported.

It did not provide other details, saying the intelligence authorities of the South and the United States are conducting a detailed analysis on the missiles' specifics.

"We strongly condemn them and call for an immediate stop," the JCS said in a text message sent to reporters as quoted by Yonhap. "Our military will maintain a solid readiness posture based on capabilities to respond overwhelmingly to any North Korean provocations."

The North appears to have fired the missiles toward a preset target on Alseom, an uninhabited island off the North's east coast, informed source told the South Korean news agency.