The missile flew 1,100km before falling into the sea, the military said, adding that it “strongly condemns” this “clear act of provocation”.
The launch comes as US Secretary of State Antony Blinken visits Seoul for talks with some of South Korea’s key leaders.
Earlier on Monday, Blinken met with acting president Choi Sang-mok, where he described the alliance between Washington and Seoul as a “cornerstone of peace and stability on the Korean peninsula”.
South Korea’s military says it has strengthened surveillance for the North’s future missile launches and is “closely sharing information” on today’s launch with the US and Japan.
Today’s launch also comes amid political chaos in South Korea, which has embroiled the country for weeks after suspended President Yoon Suk Yeol’s short-lived martial law attempt in December.
Yoon, who was stripped of his presidential powers after lawmakers voted to impeach him, now faces arrest. The constitutional court is also deliberating whether he should be removed from office.
Pyongyang previously mocked Yoon’s shock martial law declaration as an “insane act” and accused Yoon of “brazenly brandishing blades and guns of fascist dictatorship at his own people”.
The international community considers North Korea’s leader Kim Jong Un a dictator. Kim’s family has ruled the hermit nation for decades by developing and promoting a cult of personality.
The last time Pyongyang fired missiles was in November, a day before the US presidential election, when it launched at least seven short-range ballistic missiles off its east coast.
Earlier that week, the US had flown a long-range bomber during trilateral military drills with South Korea and Japan in a show of power, drawing condemnation from Kim’s sister Kim Yo Jong.
MNA/