U.S. stocks continued a rout sparked by Britain's shock vote to leave the European Union, with the Dow Jones Industrial Average falling more than 250 points after equities on Friday tumbled the most in 10 months.

Banks remained the focal point in the downdraft, with no sign of the pummeling letting up as lenders marked the worst two-day drop in almost five years. Raw-material and industrial shares also posted the steepest back-to-back slide since 2011. Sentiment was dealt another blow after S&P Global Ratings today cut the U.K.'s top credit grade by two levels.

"Today seems to be a repeat of Friday," said Ben Rozin, senior analyst and portfolio manager at Manning & Napier Advisors, which manages $37.3 billion. "We came into this year with first-quarter earnings being weak, and we were just beginning to see signs that the second quarter would be better. A big shock isn't good for confidence or investments. There's a lot of uncertainty and people weren't positioned for the vote ahead of time."

Risk assets have been under pressure since Britons voted to secede from the EU, raising concerns that an already-fragile global economic recovery will falter as trade snarls in one of the world's biggest consumer blocs. Friday's losses reversed a weekly advance in the S&P 500 and pushed the CBOE Volatility Index up 49 percent. The measure of market turmoil known as the VIX fell Monday, even as stocks continued to drop.

The U.K.'s Brexit vote left investors around the world scurrying toward safe havens for a second session after the S&P 500 on Friday fell 3.6 percent to erase its advance for the year. Investors are watching for policy action by central banks worldwide to ease the turmoil and pump liquidity into financial markets. European equities continued to bear the brunt of the selling, with the Stoxx Europe 600 Index losing 4.1 percent to its lowest since February.