WASHINGTON- U.S. President Donald Trump said on Wednesday he had ordered Treasury Secretary Steven Mnuchin to "substantially increase sanctions" imposed on Iran, amid escalating tensions between Washington and Tehran.

He did not give additional details on the move, which follows weekend attacks on oil facilities in Saudi Arabia that some U.S. officials have blamed on Iran.

(Reporting by Makini Brice and Susan Heavey) ((M.Brice@thomsonreuters.com; +1-202-310-5675; ;))