North Korea's test Saturday of what appeared to be a submarine-launched ballistic missile was "a clear violation" of UN Security Council resolutions, the United States said, warning it was watching intently.
The missile flew 30 kilometers (18 miles) but the launch in the Sea of Japan was believed to have failed, the South Korean defense ministry said.
"We closely monitor North Korean activities and the situation on the Korean peninsula, especially North Korean military activities," US State Department spokesman John Kirby said in a statement.
"Launches using ballistic missile technology are a clear violation of multiple UN Security Council resolutions.
"We call on North Korea to refrain from actions that further destabilize the region and focus instead on taking concrete steps toward fulfilling its commitments and international obligations."
North Korea has been pushing to acquire submarine-launched ballistic missile (SLBM) capability that would take its nuclear strike threat to a new level, allowing deployment far beyond the Korean peninsula and the potential to retaliate in the event of a nuclear attack.
It has conducted a number of what it says were successful SLBM tests, but experts question the claim, suggesting Pyongyang had gone little further than a "pop-up" test from a submerged platform.