The agency said the missiles were fired Wednesday into the East Sea, also known as the Sea of Japan, without “any adverse impact on the security of neighboring countries”.

The reported launch came after weeks of mounting friction over a landmine explosion along the heavily fortified border between North and South Korea.

Three South Korean soldiers were injured in the September 21 blast in the Seoul-controlled area of the Demilitarised Zone (DMZ), with both countries testing upgraded missile technology in the aftermath.

The latest testing “aimed to examine the current mobilized posture of the underwater combat systems” and served as a Navy training exercise, KCNA said.

Photos released by KCNA showed one missile blasting vertically out of the sea trailed by a thick plume of smoke. Another photo appeared to show a projectile erupting from the water at a 45-degree angle.

Other images showed a missile flying horizontally over the sea, as well as a submarine traveling on the water’s surface.

North Korea has carried out several missile launches from submarines in recent years, although its sea-based launch capabilities remain unclear.

Cruise missiles tend to be jet-propelled and fly at a lower altitude than more sophisticated ballistic missiles, making them harder to detect and intercept.

Proven submarine-launched ballistic missile capability would take North Korea’s arsenal to a new level, allowing deployment far beyond the Korean peninsula and a second-strike capability in the event of an attack.

North Korea has carried out multiple ballistic missile tests in October, most recently on Monday.

The two Koreas have engaged in a tit-for-tat series of missile tests this month, with both sides test-firing hypersonic weapons.

South Korea test-fired its first homegrown hypersonic missile last week, days after Pyongyang said it had launched an AI-assisted intermediate-range hypersonic missile.

Seoul and Pyongyang remain technically at war as the Korean conflict ended in 1953 with a truce rather than a peace treaty.