North Korea fired two ballistic missiles towards the sea off its east coast, Friday. Yonhap

North Korea fired two short-range ballistic missiles (SRBMs) into the East Sea on Friday, the South Korean military said, less than a week after its launch of two medium-range ones.

The Joint Chiefs of Staff (JCS) said it detected the launch from the Sunan area in Pyongyang at 4:32 p.m., and that the two missiles flew some 250 kilometers and 350 km, respectively. It did not provide other details.

The launch came after the South and the United States staged air drills, involving America's B-52H strategic bombers and F-22 stealth jets, on Tuesday in a show of force following the North's missile launches Sunday.

The JCS denounced Friday's launches as an act of "significant provocation" that harms peace and stability not only on the Korean Peninsula but also in the international community, and a "clear" breach of U.N. Security Council resolutions.

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

Kim Gunn, Seoul's chief nuclear envoy, held phone talks with his U.S. counterpart, Sung Kim, to condemn Pyongyang's missile launch and discuss their countermeasures, the foreign ministry said.

On Sunday, the North launched what Seoul officials called two medium-range ballistic missiles into the East Sea.

The following day, it claimed the launch was part of a military reconnaissance satellite development project, while unveiling a plan to finish preparations for its first such satellite by April next year.

Kim Yo-jong, the younger sister of North Korean leader Kim Jong-un, took umbrage Tuesday at South Korean experts doubting if the North has mastered the atmospheric reentry technology for its intercontinental ballistic missile (ICBM).

She also hinted at the possibility of the North firing an ICBM at a standard angle ― rather than a lofted one ― to prove the country's ICBM technology.

This year, the North has fired more than 60 ballistic missiles, a single-year record, as it is forging ahead with its stated weapons projects, such as developing hypersonic missiles and solid-fuel long-range ones. (Yonhap)