The round-up sets alarm bells ringing across the region and beyond. It also recalls the palace coup in June through which Mohammad bin Salman ousted his elder cousin, Mohammad bin Nayef, as heir to the throne and interior minister.
MbS, as he is known, was widely expected to follow through by, at the least, removing Prince Miteb bin Abdallah from leadership of the National Guard, a pivotal power-base rooted in the kingdom's tribes.
Other detainees include former finance minister Ibrahim al-Assaf, a board member of national oil giant Saudi Aramco; economy minister Adel Fakieh, who once played a major role in drafting reforms; former Riyadh governor Prince Turki bin Abdullah and Khalid al-Tuwaijiri, who headed the Royal Court under the late King Abdullah.
Prince Alwaleed is one of Saudi Arabia's best-known international businessmen as an investor in firms such as Citigroup and Twitter.
Bakr bin Laden, chairman of the big Saudi Binladin construction group, and Alwaleed al-Ibrahim, owner of the MBC television network, were also detained.
Some detainees were believed to be held at the opulent Ritz-Carlton hotel in the diplomatic quarter of Riyadh, sources in contact with the government told Reuters. The hotel and an adjacent facility were the site of an international conference promoting Saudi Arabia as an investment destination last month.
The detentions followed a crackdown in September on political opponents of Saudi Arabia's rulers that saw some 30 clerics, intellectuals and activists detained.
Prince Alwaleed, a flamboyant character, has sometimes used his prominence as an investor to aim barbs at the kingdom's rulers.
In December 2015, Prince Alwaleed called U.S. President Donald Trump, who was then a candidate, a "disgrace to all America" and demanded on his Twitter account that he withdraw from the election.
Trump responded by tweeting: "Dopey Prince @Alwaleed_Talal wants to control our U.S. politicians with daddy’s money. Can't do it when I get elected."
In November 2016 Prince Alwaleed put aside the clash with Trump and embraced him as the U.S. president-elect, saying he was heartened by reports that Trump had appeared to delete online references to his proposed ban on Muslims.
