North Korea fired a ballistic missile towards the sea off its east coast, South Korea's Joint Chiefs of Staff said in a statement on Sunday.
The missile is believed to have already fallen, according to Japan's Defense Ministry.
The last time Pyongyang tested its ballistic missile was in November.
South Korean President Lee Jae Myung is making a state visit to China starting from Sunday, where experts say he might ask Beijing to facilitate dialog with North Korea.
North Korean leader Kim Jong Un called for more than double the production capacity of tactical guided weapons on his latest visit to a munitions factory, North Korea's state media reported on Sunday.
Kim Jong Un visits weapons, submarine factories
In recent weeks, Kim has made a series of visits to factories that build weapons, as well as to a nuclear-powered submarine, and has overseen missile tests ahead of this year's Ninth Party Congress of the Workers' Party, convened to set out major policy goals.