Two members of the Saudi royal family will testify on the 9/11 attacks in the US.

US federal judge Sarah Netburn has ruled that members of the Saudi royal family and other witnesses, including current and former government officials, must testify.

Some relatives of 9/11 victims claim that Saudi Arabian agents knowingly supported al-Qaeda and its then-leader, Osama bin Laden, prior to the 9/11 attacks that left nearly 3,000 people dead.

 The families of the victims are demanding billions of dollars in compensation.