The rogue nation fired the unidentified projectile early on Thursday from an area near Wonsan on North Korea’s eastern coast.
The Joint Chiefs of Staff told South Korea’s Yonhap News Agency: “Our military is monitoring the situation in case of additional launches and maintaining a readiness posture.”
It comes after North Korea’s leader Kim Jong-un met US President Donald Trump at the demilitarised zone (DMZ) last month.
The pair agreed to resume stalled nuclear talks.
Their joint Hanoi summit in February broke down with no agreement reached.
It followed their historic first meeting in Singapore in June 2018.
This is a breaking story. More to follow.
source: express.co.uk