North Korean leader Kim Jong-un paid visits to front-line military units near the western sea border on Monday, calling for troops to throw all enemies into a "cauldron," break their "waists" and cut their "windpipes."

The visit to the Wolnae Islet Defense Detachment and a long-range artillery sub-unit of KPA Unit 641 near the South's western border island of Baengnyeong came as South Korean and U.S. forces kicked off annual military drills that Pyongyang denounces as a rehearsal for invasion.

"A guy who is fond of playing with fire is bound to perish in flames, all the enemies quite often playing with fire in the sensitive hot spot should be thrown into a cauldron once I issue an order," Kim said during the visit to the Wolnae unit, according to the Korean Central News Agency.

"Once an order is issued, you should break the waists of the crazy enemies, totally cut their windpipes and thus clearly show them what a real war is like."

During the visit to the artillery unit, Kim told the troops to "blow up the headquarters" of South Korean Marines stationed on the island of Baengnyeong "through merciless firepower strikes if the enemies ... make a provocation," KCNA said. (Yonhap News)