North Korea has fired three ballistic missiles off its east coast in a show of force timed to coincide with the G20 summit in China, Seoul has said.
North Korea regularly engages in missile and rocket tests, especially when the world's eyes are turned to Northeast Asia.
World leaders have gathered for the G20 summit of advanced and emerging economies in the city of Hangzhou in eastern China, which is the North's only major ally.
On Monday on the sidelines of the summit, South Korean President Park Geun-hye criticised the North for what she called provocations that are hurting Seoul-Beijing ties.
South Korea's Joint Chiefs of Staff said the three missiles, launched from the western North Korean town of Hwangju, flew across the country before splashing in the waters off its east coast, but officials did not describe the range of the missiles.
The launch comes four days before the 68th anniversary of the founding of North Korea's government, and days after South Korean and US troops ended annual joint summer military drills, which North Korea regularly describes as a dress rehearsal for invasion.
Last month, worries about the North's weapons programmes deepened after a missile from a North Korean submarine flew about 310 miles, the longest distance achieved by the North for such a weapon.
The UN Security Council in late August strongly condemned four North Korean ballistic missile launches in July and August. It called them "grave violations" of a ban on all ballistic missile activity.