One daily compares the act to a Marx Brothers comedy.
Morocco's King Mohammed comes in for special criticism after the Moroccan flag was raised on the islet of Perejil (Parsley).
He is called "a crowned dictator" and "an inexpert and doubt-filled monarch".
In Morocco, in marked contrast, confines its reports to the official statement that the territory is within the country's territorial waters and the move was aimed at tackling terrorism and illegal immigration.
"Morocco goes too far" says an editorial in ABC. "Rabat's decision has the aim of straining to the utmost bilateral relations already seriously damaged following the withdrawal of the North African nation's ambassador last October."
ABC says the Moroccan provocation "behind which emerges the figure of Mohammed VI" represents "an intolerable violation of the most basic norms of good neighbourliness and the practical sense of diplomacy".
Provocation
The violation of Spanish sovereignty is "a matter of the utmost seriousness" and "deserves a response that goes beyond the mere recovery of the territory".
"Rabat's umpteenth provocation now requires a response which will make the king of Morocco see that bilateral relations are not a game and cannot be left to the whim of an inexpert and doubt-filled king."
El Mundo calls the act "Mohammed's provocation".
"The absolute lack of strategic, economic or geopolitical interest of the islet of Perejil turns the invasion of it by Morocco into an histrionic event more appropriate to the Marx brothers' film Duck Soup than relations between two civilized countries at the beginning of the 21st century."
El Mundo describes it as "this poor imitation of the taking of the Malvinas [Falklands] by the Argentine military junta two decades ago", a "desperate measure" aimed at diverting attention from internal problems.
"This is the only thing that a pathetic Mohammed VI is capable of offering his subjects on the occasion of his long announced marriage" rather than political reform or economic development.
"This frivolous monarch seems determined to promote a strategy of tension which will serve as a smoke screen to the Moroccan people's growing disappointment on seeing their hopes of change dashed."
Describing the king as "this anachronistic crowned dictator", El Mundo calls for the Spanish government to "preserve its sangfroid".
"The islet of Perejil is not even worth the fuel of the patrol vessels that have been sent."
"But one cannot ignore the gravity of this hostile act on the symbolic level. The king of Morocco has chosen the path of confrontation with one of the big European democracies and that must have a serious cost for him," El Mundo concludes.
Missed opportunity
The influential El Pais says Morocco missed an opportunity to improve relations with Spain by failing to invite King Juan Carlos and Queen Sofia to his wedding.
The daily details the diplomatic difficulties between the two countries, including what it says was Rabat's surprise recall of its ambassador to Madrid late last year.
"The penultimate in the chapter of incidents between Rabat and Madrid was the marriage of Mohammed VI, to which the Spanish Royal Family was not invited - nor indeed were Europe's other royal families - which squandered an opportunity to re-establish full relations between the two countries."
BBC Monitoring, based in Caversham in southern England, selects and translates information from radio, television, press, news agencies and the Internet from 150 countries in more than 70 languages.