Pyongyang is demanding Seoul pay at least $1 billion in compensation for allegedly torturing North Korean spies and prisoners of war formerly held in South Korea.
North Korea's official KCNA news agency says the government submitted its claim for damages to South Korea's Human Rights Commission Friday.
Pyongyang's complaint involves 63 North Koreans freed by South Korea in 2000, and sent back to the North after decades of detention. Seoul agreed to release them after a reconciliation summit between the two Koreas.
North Korea says the prisoners were subjected to physical and mental torture, and held in solitary confinement for refusing to renounce their ideology.
Pyongyang has also faced international criticism for allegedly torturing prisoners. Seoul says hundreds of South Korean prisoners are still being held by the North.
Some information for this report provided by AFP, AP and Reuters.