DUBAI (BLOOMBERG, AFP) - Prince Alwaleed bin Talal is still very wealthy, but even the mega-rich would balk at losing more than US$1 billion in 48 hours.

His net worth fell to US$17.8 billion after the market value of the Saudi investment firm he founded plummeted US$1.3 billion this week. Kingdom Holding's stock closed on Monday at the lowest level since December 2011.

Alwaleed is among dozens of princes, ministers and current or former senior officials who were arrested on Saturday night (Nov 4) on orders from a newly established anti-corruption committee headed by Crown Prince Mohammed bin Salman. The detainees include three of the country's richest people.

The purge underscores an unprecedented restructuring of the kingdom as Prince Mohammed steps up a dramatic reform drive for a post-oil era while consolidating power before his eventual succession as king.

"All those suspected... will have full access to legal resources, and the trials will be held in a timely and open manner," Attorney General Sheikh Saud al-Mojeb said in a statement on Monday, describing the crackdown as "phase one".

"A great deal of evidence has already been gathered, and detailed questioning has taken place," he added, without specifying a timeframe for the trials.

Saudi-owned Al-Arabiya television reported that 11 princes, four current ministers and dozens of ex-ministers were arrested as the commission launched a probe into old cases such as floods that devastated the Red Sea city of Jeddah in 2009.

Saudi forces have grounded private jets at airports, possibly to prevent high-profile figures from leaving the country, an aviation source told AFP. Bank accounts of those arrested will be "frozen" and any assets related to the corruption cases will be registered as state property, the information ministry said.