AT least 19 North Korean sailors were killed when a naval vessel sank during "combat duties" off the east coast last month, state media said, in a rare revelation by the impoverished and reclusive country.

South Korean media said the ship sank during a drill, and North Korea's KCNA state news agency showed images of leader Kim Jong Un laying flowers at the foot of a memorial to the dead.

"Submarine chaser No 233 fell while performing combat duties in mid-October," KCNA said.

The article did not specify what operation it was undertaking. Information in North Korea is strictly controlled, and accidents are rarely publicly admitted or closely covered by state media.

The country's official media did not say how many died in the accident, but said Mr Kim had ordered "measures to find all their bodies", suggesting a high death doll.

A South Korean newspaper said the ship sank during a drill, killing scores of sailors, and that two vessels were involved, quoting an unnamed military source.

Pyongyang was blamed for sinking a South Korean navy ship in 2010, leaving 46 sailors dead.