North Korea's Kim Jong Un inspected a tank unit which once invaded Seoul during the Korean War, state media reported Monday, with Pyongyang's leader calling for ever greater preparations for combat.

Inter-Korean relations are at one of their lowest points in years, with Kim's military recently conducting a string of banned weapons tests, including launching a ballistic missile and staging a ground test of a "new type" of hypersonic missile engine.

Kim visited the Seoul Ryu Kyong Su Guards 105th Tank Division on Sunday, the official Korean Central News Agency said, with images in state media showing him apparently reviewing South Korean attack plans.