US. media reported on Saturday that North Korea has been searching for one of its submarines which has reportedly been missing for days off its east coast.
The submarine may be adrift under the sea or have sunk, perhaps after a technical problem during an exercise, CNN quoted US officials with intelligence of secret US monitoring of the North's activities as saying.
File footage released by North Korea's state-run television KRT in 2014 and 2015 show North Korean leader watching a submarine exercises off the coast of North Korea.
North Korea has said it is developing submarine-launched ballistic missiles although doubts about that were raised after Western experts said publicly released footage of tests appeared to be fake.