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Aug 2 (Reuters) - European shares tumbled to near two-week lows on Wednesday, with technology and auto stocks leading losses, as investors across the globe fled riskier assets after a surprise downgrade on U.S. credit rating by Fitch.

The pan-European STOXX 600 index fell 1.1% by 0708 GMT, touching its lowest level since July 20.

U.S. futures slid more than half a percent and bond prices rose after rating agency Fitch on Tuesday downgraded U.S. debt rating, citing fiscal deterioration over the next three years and repeated down-the-wire debt ceiling negotiations that threaten the government's ability to pay its bills.

The STOXX 600 fell about 1% on Tuesday, its worst day in nearly a month, after weak factory activity data worldwide raised concerns of an economic slowdown.

Among single stocks, U.S.-German medical device maker Siemens Healthineers dropped 5.4% after posting an unexpected drop in quarterly operating profit over diminishing COVID-19 test demand and delivery delays at cancer treatment specialist Varian.

German fashion house Hugo Boss fell 4.1% even as it raised its full-year outlook.

(Reporting by Sruthi Shankar in Bengaluru; Editing by Sherry Jacob-Phillips)