North Korea conducted an "underwater launching drill" of strategic cruise missiles off its eastern coast, the country's official media reported Monday.

The Korean Central News Agency said an 8.24 Yongung submarine launched two cruise missiles in an "underwater-to-surface offensive" operation drill Sunday morning, a day before the South Korean and U.S. militaries are scheduled to start their "Freedom Shield" joint exercise.

Photo shows North Korea's "underwater launching drill" of strategic cruise missiles on March 12, 2023. (KCNA/Kyodo)

The South Korean military said Monday it detected at least one missile launched from a North Korean submarine the previous day. Seoul's intelligence agency said recently Pyongyang may test-fire an intercontinental ballistic missile in protest over the joint exercise.

In Sunday's drill by the submarine units that constitute part of North Korea's nuclear deterrent, the cruise missiles successfully hit a target on the sea after traveling "1,500-kilometer eight-shaped flight orbits," according to KCNA.