The unidentified missile was fired from near the North Korean coastal city of Wonsan, Seoul's joint chief of staff said.
News of the launch comes as US President Donald Trump seeks tougher sanctions against the isolated nuclear-armed regime, which is on a quest to develop a missile capable of reaching the continental United States.
The unidentified missile was fired from near the North Korean coastal city of Wonsan, Seoul's joint chief of staff said.
South Korea's new president, Moon Jae-In, has ordered a meeting of the national security council to assess the launch, Yonhap reported.
North Korean leader Kim Jong-Un has sought to ramp up the country's weapons programme.
Pyongyang has carried out two atomic tests and dozens of rocket firings since the start of last year, triggering UN sanctions.
US President Donald Trump has been briefed the reported missile test, a White House official said on Sunday.
"The United States government is aware," the White House official said. "The president has been briefed."
