North Korea fired one short-range ballistic missile (SRBM) into the East Sea on Sunday, South Korea's military said.

The Joint Chiefs of Staff said it detected the launch from the Ryongsong area in Pyongyang at 2:50 a.m., adding the missile flew some 400 kilometers before splashing into the sea.

It appears to be another response to Seoul's test launch of a homegrown solid-propellant space rocket on Friday, according to North Korea observers.

On Saturday morning, the North shot three SRBMs from Chunghwa County, just south of Pyongyang, into the East Sea.

In its own announcement, meanwhile, the North said it fired "super-large" caliber artillery shells on Saturday and Sunday in sample tests.

The multiple rocket launcher system has been presented to the ruling Workers' Party of Korea during its key plenary session, the KCNA reported.

The North's leader Kim Jong-un said the 600-mm super-large shells can be loaded with tactical nuclear warheads with the entire South in range, the KCNA added.

The South's military categorizes such super-large multiple rocket launchers as SRBMs, given their ranges and trajectories.

The JCS denounced the North's latest missile launch 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 UN Security Council resolutions.

"Our military will maintain a solid readiness posture based on capabilities to respond overwhelmingly to any North Korean provocations, "the JCS said in a text message sent to reporters.

The US Indo-Pacific Command also said in a statement that the firing highlights the "destabilizing impact" of North Korea's unlawful weapons programs.

The North launched around 70 ballistic missiles last year alone. (Yonhap)