North Korea has fired at least two unidentified projectiles from an area near Wonsan, on the country's eastern coast, South Korea's Joint Chiefs of Staff have said.
The projectiles flew about 430km, the Joint Chiefs of Staff said, but did not elaborate further.
The United States confirmed the incident, saying they had detected one "short range" projectile.
"I can confirm that it was... short-range" a US official told AFP, speaking on condition of anonymity.
He did not say when the launch was carried out.
It would be the first launching of projectiles reported since US President Donald Trump and North Korean leader Kim Jong-un met at the demiliterised zone (DMZ) between the two Koreas at the end of June.
North Korea's last weapons test was in May, which included both short-range missiles as well as smaller rockets.
At the time, Mr Kim oversaw the first flight of a previously untested weapon - a relatively small, fast missile that experts believe will be easier to hide, launch and manoeuvre in flight.
Yesterday, state news agency KCNA reported that Mr Kim inspected a large, newly built submarine, accompanied by missile programme leaders.
It potentially signalled continued development of a submarine-launched ballistic missile (SLBM) programme.
Denuclearisation talks between North Korea and the United States have stalled after a second summit between Mr Trump and the North Korean leader in Vietnam in February broke down.