In remarks unprecedented in modern-day Spain, King Felipe VI told the nation in a televised address that the separatist Government in Catalonia had acted totally outside law and democracy by staging a disputed referendum on independence.
The King charged: They have meant to fracture Spain.
Sitting at his desk in Zarzuela Palace in Madrid, the King said the central Government must ensure constitutional order in Catalonia.
The Spanish constitution describes the monarch as head of state and commander in chief, although the King serves a largely symbolic role these days. He traditionally addresses the nation during the Christmas holidays - not during political crises.
His words are likely to bolster the central Governments case that the Catalan separatists have gone too far - and may signal new get-tough measures by Madrid against the Barcelona rebellion.
Trade unions in Catalonia led a powerful general strike that shut down businesses, highways and schools in a mass protest against police violence during the regions chaotic independence vote. Huge crowds poured through the streets of Barcelona.
Demonstrators said they were appalled by images of Spains national police and civil guard, sent to shut down the referendum, beating voters with rubber batons and dragging them away from ballot boxes. The marchers chanted, Occupying forces get out!
The raw emotions - and the stark divisions between the separatists and those who want to keep Spain united - are only growing. Paula Miranda, a university student, said: I felt lots of impotence and rage. I was not expecting this.