DUBAI, Sept 29 (Reuters) - The Saudi riyal fell moderately against the U.S. dollar in the forwards market on Thursday after the U.S. Congress voted to allow relatives of victims of the Sept. 11 attacks to sue Saudi Arabia.

The Senate and House of Representatives voted overwhelmingly on Wednesday to override President Barack Obama's veto of legislation permitting such lawsuits. The law grants an exception to the legal principle of sovereign immunity in cases of terrorism on U.S. soil, clearing the way for attempts to seek damages from the Saudi government. ID:nL2N1C41EC

One-year dollar/riyal forwards SAR1Y= , which are trades scheduled to take place 12 months from now, were at 550 points in early trade, up from Wednesday's close of 330 points. They rose as far as an eight-week high of 625 points.

The Saudi riyal SAR= is pegged at 3.75 to the dollar in the spot market, so banks often use the forwards market to hedge against risks.

Five-year Saudi credit default swaps SAGV5YUSAC=MG , used to insure against the risk of a sovereign debt default, rose slightly to 157 points from 152. The price of state-controlled Saudi Electricity Co's 5110.SE April 2023 dollar Islamic bond SASUKCBAA45= , one of the few outstanding international bonds from Saudi Arabia, did not move significantly.

(Reporting by Andrew Torchia; Editing by Toby Chopra) ((andrew.torchia@thomsonreuters.com; +9715 6681 7277; Reuters Messaging: andrew.torchia.thomsonreuters.com@reuters.net))