The US Department of Justice is investigating two transactions, probing whether Prince Turki bin Abdullah bin Abdel Aziz - a wing commander in the Saudi air force who was recently made deputy governor of the capital city of Riyadh - was paid illicit fees by Barclays, according to six people familiar with the investigation.
The revelation shines another unwelcome spotlight on Barclays' business dealings in the Middle East.
The bank remains under investigation in the US and UK over the terms of a crucial capital injection by Qatar in 2008.
In addition to the alleged payment connected to the 2009 award of a Saudi banking license from the CMA, the local regulator - as reported by the Financial Times last November - Barclays is also being investigated over a separate alleged transaction linked to the prince.
This was in connection with earlier attempts by the bank to recover a large loan on which the borrower had defaulted in 2002.
The US authorities' enquiries threaten further damage to the kingdom's international ties.
Its relations with the UK and the US have been under strain for much of the last decade over prosecutors' inquiries into BAE Systems and its dealings with another Saudi prince. The US authorities went on to fine BAE $400m in 2010 for improper business dealings in the kingdom and in Europe.