RIYADH, Saudi Arabia — Saudi Arabia’s heir to the throne is overseeing an unprecedented wave of arrests of dozens of the country’s most powerful princes, military officers, influential businessmen and government ministers – some potential rivals or critics of the crown prince now consolidating his power.

Among those taken into custody overnight Saturday in the purported anti-corruption sweep were billionaire Prince Alwaleed bin Talal, one of the world’s richest men with extensive holdings in Western companies, as well as two of the late King Abdullah’s sons.

The arrest of senior princes upends a longstanding tradition among the ruling Al Saud family to keep their disagreements private in an effort to show strength and unity in the face of Saudi Arabia’s many tribes and factions. It also sends a message that the 32-year-old crown prince, Mohammed bin Salman, has the full backing of his father, King Salman, to carry out sweeping anti-corruption reforms targeting senior royals and their business associates, who have long been seen as operating above the law.

Reports suggested those detained were being held at the Ritz Carlton in Riyadh, which only days earlier hosted a major investment conference that the crown prince attended with global business titans. A Saudi official said other five-star hotels across the capital were also being used to hold some of those arrested.

The Ritz Carlton had no availability for bookings until Dec. 1 – a possible sign that an investigation of this scale could take weeks. Marriott International said that it is currently evaluating the situation at the Ritz-Carlton in Riyadh, but declined to comment further, citing privacy concerns.

A Saudi government official with close ties to security forces said on condition of anonymity that 11 princes and 38 others were being questioned.

The surprise arrests were immediately hailed by pro-government media outlets as the clearest sign yet that Prince Mohammed is keeping his promise to reform the country, wean its economy from its dependence on oil and liberalize some aspects of the ultraconservative society.

The kingdom’s top council of clerics issued a public statement overnight saying it is an Islamic duty to fight corruption – essentially giving religious backing to the high-level arrests.

It’s unclear if the U.S. had any advance word of the arrests. President Trump’s son-in-law and White House adviser Jared Kushner and others made an unannounced trip recently to Riyadh. Earlier Saturday, Trump said he spoke to King Salman, though the White House readout of that call did not include any reference to the impending arrests.

The Saudi government says the arrests are part of a wider effort to increase transparency, accountability and good governance – key reforms needed to attract greater international investments and appease a Saudi public that has for decades complained of rampant government corruption and misuse of public funds by top officials.