ISTANBUL 

US stocks ended lower Wednesday, with the Nasdaq falling more than 2% after Fitch Ratings downgraded the US's long-term foreign currency issuer default rating to "AA+" from "AAA." 

The tech-heavy index plummeted 310 points, or 2.17%, to finish the day at 13,973, marking its worst single-day performance since February.

The Dow Jones Industrial Average fell 348 points, or 0.98%, to end the session at 35,282. The S&P 500 was down 63 points, or 1.38%, to close at 4,513.

Fitch said Tuesday that the US's rating change reflects expected fiscal deterioration over the next three years and a high and growing general government debt burden as well as debt limit standoffs and last-minute resolutions.

US Treasury Secretary Janet Yellen, as a response, said earlier Wednesday that the rating decision is "puzzling" and "entirely unwarranted," adding it is based on a "flawed assessment."

The VIX volatility index, also known as the fear index, jumped 15.5% to 16.09. The 10-year US Treasury yield, meanwhile, rose 0.8% to 4.082%.

The dollar index added 0.34% to 102.65, while the euro fell 0.41% to $1.0937 against the greenback.

Precious metals were in negative territory, with gold trimming 0.46% to $1,935 per ounce and silver decreasing 2.4% to $23.71.

Oil prices were down around 1.8%, with global benchmark Brent crude at $83.45 per barrel and US benchmark West Texas Intermediate crude at $79.75.