Saudi Arabia said on Thursday that it had concluded a crackdown on high-level corruption that began 15 months ago with the detention of hundreds of prominent businessmen and former officials at the Ritz-Carlton in the capital.

The purge helped confirm the unrivaled authority of Mohammed bin Salman, the crown prince and de facto ruler of the kingdom, and critics have called it a power grab. Saudi Arabia has disclosed little about the proceedings, and associates of several people caught up in the crackdown have said the detentions were arbitrary, lacking in any judicial process and frequently targeted foes of the prince.

Associates of many of those detained have also said they were subjected to torture and physical abuse, then coerced into turning over large sums of money or other assets in exchange for their release.

Supporters of the crown prince defend the crackdown as a necessary push to shock the Saudi elite out of longstanding habits of graft and self-dealing. The kingdom has denied any physical abuse.