Reuters wrote Isolated North Korea marked the 70th anniversary of its ruling Workers' Party on Saturday with a massive military parade overseen by leader Kim Jong Un, who said his country was ready to fight any war waged by the United States.

The young leader was accompanied by senior Chinese Communist Party official Liu Yunshan, with whom he was seen speaking throughout the event and occasionally shared laughs, and flanked by senior North Korean party and military officials.

"The party's revolutionary armament means we are ready to fight any kind of war waged by the U.S. imperialists," Kim said in a speech strikingly more forceful than previous public comments, praising the feats of past leaders and the ruling party.

Kim's speech was followed by troops marching in formation, first by a corps of soldiers dressed in the style of the revolutionary force that fought Japan during World War Two, and then a procession of military might rolling past the square.

A battery of the North's intercontinental ballistic missiles was the highlight of the weapons display, although they are not known to have been successfully tested.