North Korea fired multiple cruise missiles towards the sea off its west coast on Wednesday, South Korea's Joint Chiefs of Staff said, in the latest sign of heightened tensions on the Korean peninsula.
The missiles were fired at around 7:00 am (2200 GMT on Tuesday) and the launches were being analysed by South Korean and US intelligence, the JCS said in a statement.
Further activities by the North were being monitored, the JCS said.
The latest firing of missiles by Pyongyang comes as the South Korean Navy's special warfare unit was taking part in training along the east coast in Gangwon Province bordering the North for 10 days.
The training was aimed at strengthening operational readiness following North Korea's recent artillery firing near a disputed maritime border and weapons tests, the JCS said.
Pyongyang said it tested a solid-fuel hypersonic missile with intermediate-range earlier this month in a move that was condemned by the United States, South Korea and Japan.
The isolated North has also demolished a major monument in its capital that symbolised the goal of reconciliation with South Korea on the orders of leader Kim Jong Un, who last week called the rival a "primary foe" and said unification was no longer possible.
Satellite imagery of Pyongyang on Tuesday showed that the monument, an arch symbolising hopes for Korean reunification which was completed after a landmark inter-Korea summit in 2000, was no longer there, according to a report by NK News, an online outlet that monitors North Korea.
Reuters could not independently confirm that the monument, known informally as the Arch of Reunification, had been demolished.