North Korea launched about ten ballistic missiles toward the Sea of Japan on Saturday, South Korea’s Joint Chiefs of Staff said, as Seoul continues annual joint military exercises with the United States that began on Monday.

In a statement, the Joint Chiefs said South Korean forces detected “about ten unidentified ballistic missiles launched from the Sunan area in North Korea toward the East Sea,” the Korean name for the Sea of Japan.

The launches were detected at around 13:20 local time (04:20 GMT), the statement added.

The development comes after North Korean state media reported on Wednesday that leader Kim Jong Un and his teenage daughter oversaw tests of strategic cruise missiles launched from a warship.

Pyongyang has also threatened to respond to the joint military drills between the United States and

South Korea.