Kingdom Holding Co., the investment company of Prince Alwaleed Bin Talal, has raised its stake in Citigroup Inc. to 2.2% after buying a $450 million stake from the Saudi billionaire.

Kingdom previously owned a 1.63% holding in the Wall Street firm, according to a Saudi stock market filing on Wednesday, which didn’t give further details.

Alwaleed is one of the highest profile Saudi investors after taking stakes in companies such as Citigroup and Apple. He has supported Crown Prince Mohammed bin Salman’s modernization efforts, including giving women the right to drive.

Alwaleed’s relationship with Citigroup dates back to 1991, when he invested $590 million to become the bank’s largest shareholder.

His stature on the global investment stage has faded since 2017, when he was imprisoned along with hundreds of other businessmen and officials as part of the crown prince’s anti-corruption drive, though no formal charges were ever presented. He was released after 83 days in Riyadh’s Ritz Carlton hotel. Neither he nor the government disclosed details of the agreement, which Alwaleed described as a “confirmed understanding.”

In 2022, Saudi Arabia’s sovereign wealth fund bought a $1.5 billion stake in Kingdom Holding. Alwaleed has a 78.1% holding in the investment firm, with the remaining 5% of the stock listed on the Saudi bourse.

Kingdom Holding also holds a stake in Twitter Inc., and Alwaleed backed Elon Musk’s acquisition of the company.