North Korea has fired what appear to be short-range missiles into the sea off its east coast, according to South Korean media.

The report from Yonhap news agency cited South Korea’s military as saying the North fired several “unidentified projectiles” early Saturday morning Korea time.

The South Korean Office of the Joint Chiefs of Staff said they believe the launch was a test and they were trying to determine whether the object was a ballistic missile.

The missile launch comes at a time of increased tension between the nuclear-armed nation and the United States.