North Korea fired two ballistic missiles on Wednesday morning, just days after Pyongyang's previous launch.
According to the South's military, the unidentified warheads landed in the sea to the east of the Korean Peninsula.
In a statement, the U.S. military's Indo-Pacific Command said the missile launch posed "no immediate threat" to U.S. personnel or allies.
Over the weekend, Pyongyang carried out what it said were successful tests of a long-range cruise missile, a weapon with probable nuclear capabilities.
North Korea's latest round of missiles came as nuclear envoys of South Korea, Japan and the United States were meeting in Tokyo this week.
It drew anger from Japanese Prime Minister Yoshihide Suga.
"The launch of a possible ballistic missile threatens the peace and security of our country and the region, and is outrageous."
The latest launch on Wednesday came just as China's Foreign Minister Wang Yi was in Seoul, to discuss North Korea's earlier cruise missile test and the stalled 'denuclearization' talks between Washington and Pyongyang.
South Korean President Moon Jae-in had reportedly asked for China's help to restart dialogue with the North, which has been unresponsive to offers from the South or the U.S. to talk or engage in humanitarian aid.
Wang told reporters that "not only North Korea" but all parties should work in ways to resume dialogue, and promote peace and stability on the Korean peninsula.
The two ballistic missile tests are North Korea's first since March this year.
Negotiations with former U.S. President Donald Trump to urge Kim Jong Un to dismantle his nuclear arsenal in return for U.S. sanctions relief have stalled since 2019.