North Korea fired a ballistic missile on Sunday, South Korea's defence ministry said, the first since Donald Trump became US president.
The missile, launched around 7:55 am (22:55 GMT Saturday) from Banghyon air base in the western province of North Pyongan Province, flew east towards the Sea of Japan, it said.
"The concrete type of the ballistic missile has yet to be identified", a defence ministry spokesman told AFP.
But Yonhap news agency said the South Korean military suspected the North might have been testing a intermediate-range Musudan missile.
North Korea in October last year tested Musudan missiles twice that were fired from the same airbase.