The stunning breach of protocol, did shut up the socialist revolutionary. For about two seconds. Then he regained his voice. However brief, it was a moment Chávez's detractors have dreamed of: the comeuppance, as they see it, of a motormouth autocrat who regularly obliges all of Venezuela's television stations to broadcast his marathon speeches.

Venezuela's opposition gleefully portrayed Saturday's encounter at an Ibero-American summit in Santiago, Chile, as a humiliation. People gave each other the high-five and replayed the scene over and over. The president's supporters were indignant and said the king was the one humiliated because he lost his temper.

Cuba's Fidel Castro issued a statement backing his ally. "Chávez's criticism of Europe was devastating."

Chávez prompted the row by calling the former Spanish prime minister, José María Aznar, a "fascist" who supported a 2002 coup against him. When the current Spanish prime minister, José Luis Rodríguez Zapatero, defended his predecessor as a legitimately elected leader, Chávez repeatedly interrupted, even though his microphone was off.

It was at this point that the king, seated beside Zapatero, intervened. He used the familiar form "tu" rather than the more formal "usted".

Most Spanish newspapers applauded the rebuff. "The king fulfilled his role, given that the Venezuelan president crossed the line," said El Pais.

Chávez complained of disrespect by a hereditary leader. "The king is a head of state like me, only that I have been elected three times with 63% support."