North Korea fired a short-range missile into the sea on Saturday, the 15th time it has launched rockets this year, the South's Yonhap news agency reported.
South Korea's Joint Chiefs of Staff in a statement said the North "fired a short-range missile presumed to be a Scud-type one into the East Sea" at 09:40 pm (12:40 GMT).
The missile, with an estimated range of 500 kilometres (300 miles), was launched in a northeastern direction from Jangsan Cape in North Korea's western coastal region.
"We are analysing the motive of its missile launch, and we have maintained high-level readiness against its possible additional firing," Yonhap quoted the JCS statement as saying.
Pyongyang had not imposed a no-fly, no-sail zone ahead of the launch, which was the sixth ballistic missile firing this year, the news agency said.