Oil prices are rising after a fresh tanker attack in the Persian Gulf, putting a damper on stocks.

Benchmark Brent crude prices are up around 4% and are heading for their highest close since mid-September. The U.S. had recently succeeded in restoring crude shipments through the Strait of Hormuz, but Iran appears to have intensified its attacks on tankers in response, putting oil markets on edge.

Production cuts in the Gulf of Mexico, prompted by a hurricane, aren't helping either.

Rising energy prices are weighing on U.S. stocks, which are slipping for a second day after the S&P 500 and Nasdaq hit records Tuesday.