North Korea has repeated its calls for South Korea to return its restaurant workers who defected to the South in April from China.

The North's official Korean Central News Agency(KCNA) reported on Monday that the North's Red Cross recently made the demand in a letter sent to its South Korean counterpart.

It strongly criticized Seoul for making an announcement that the 13 North Korean restaurant workers were released from South Korean state custody after months of resettlement education, calling it a dirty plot to cover up a mass abduction.

Pyongyang has reportedly threatened that Seoul will reap irreparable consequences unless it returns the North Korean citizens.