North Korea fired several short-range missiles into the sea off its east coast early on Saturday, South Korea and the U.S. military said, as the two allies conducted annual joint military drills that the North denounces as preparation for war.
The U.S. military's Pacific Command said it had detected three short-range ballistic missiles, fired over a 20 minute period.
One appeared to have blown up almost immediately while two flew about 250 km (155 miles) in a northeasterly direction, Pacific Command said, revising an earlier assessment that two of the missiles had failed in flight.
The test came just days after senior U.S. officials praised North Korea and leader Kim Jong Un for showing restraint in not firing any missiles since late July.
The South Korean Office of the Joint Chiefs of Staff said the projectiles were launched from the North's eastern Kangwon province into the sea.
Later on Saturday, the South Korean Presidential Blue House said the North may have fired an upgraded 300-mm calibre multiple rocket launcher but the military was still analyzing the precise details of the projectiles.
Pacific Command said the missiles did not pose a threat to the U.S. mainland or to the Pacific territory of Guam, which North Korea had threatened earlier this month to surround in a "sea of fire".
Tensions had eased somewhat since a harsh exchange of words between Pyongyang and Washington after U.S. President Donald Trump had warned North Korean leader Kim Jong Un he would face "fire and fury" if he threatened the United States.
North Korea's last missile test on July 28 was for an intercontinental ballistic missile designed to fly 10,000 km (6,200 miles). That would put parts of the U.S. mainland within reach and prompted heated exchanges that raised fears of a new conflict on the peninsula.
Japan's Chief Cabinet Secretary Yoshihide Suga said the missiles did not reach its territory or exclusive economic zone and did not pose a threat to Japan's safety.