When an intelligence agency arranges to disseminated fake news it is called "disinformation" and it is a subset of what is referred to as covert action, basically secret operations run in a foreign country to influence opinion or to disrupt the functioning of a government or group that is considered to be hostile.
During the Cold War, disinformation operations were run by many of the leading players in both the North Atlantic Treaty Organization and in the opposition Warsaw Pact. Sometimes the activity and the sponsorship were clearly visible, as when Radio Free Europe and Radio Moscow would exchange barbs about just how bad daily life was in the opposition alliance. Sometimes, however, it took the form of clandestinely placing stories in the media that were clearly untrue but designed to shift public perceptions of what was taking place in the world. The Vietnam War provided a perfect proxy playing field, with stories emanating from the U.S. government and its supporters presenting a narrative of a fight for democracy against totalitarianism while the Communist bloc promoted a contrary tale of colonial and capitalist oppression of a people striving to be free.