They seemed untouchable. The head of a huge construction conglomerate. A prince who led Saudi Arabia’s elite national guard. A billionaire investor who was one of the richest people in the world.

But in one breathtaking stroke, the men were detained by the Saudi authorities in a purge that began Saturday night and swept up some of the most powerful and recognizable names in the country, including members of the Saudi royal family, cabinet ministers, titans of media and industry, and former officials. The detainees included Prince Alwaleed bin Talal, a wealthy investor who owns major stakes in such companies as Twitter and Citigroup, according to an associate of his family.

On Sunday, Saudi officials cast the arrests as the first shot in a battle against the country’s notorious and deeply rooted corruption, and as part of a broader effort by the country’s young and ambitious crown prince, Mohammed bin Salman, to refresh the stagnating Saudi state.

For others, though, the detentions seemed more like the continuation of a process that had been accelerating over the past two years: the ruthless consolidation of power by the crown prince before his father, King Salman, dies or abdicates the throne. That process — which included eliminating critics and rivals, but also elite figures who presided over independent power centers — amounted to a radical restructuring of the Saudi order, analysts said.