North Korea claims to have successfully tested a long-range missile engine, giving it the ability to launch a nuclear strike on the United States.
North Korean state media released a video of leader Kim Jong-un supervising the launch.
There have been increased tensions since North Korea claimed to have tested its first hydrogen bomb and fired a long-range rocket last month.
South Korea and the U.S. recently carried out their largest ever military drill , viewed as an aggressive act by North Korea
Although North and South Korea signed an armistice more than sixty years ago, the two countries are still technically in a state of war.