U.S. stocks extended declines Thursday, with the Dow briefly approaching an 700-point slide, as investors continue to test the resiliency of risk markets amid the biggest global sell-off since February.

The CBOE's key risk indicator, known by its trading symbol (VIX.X) , jumped to a February high of 28.8 points as the Dow Jones Industrial Average tumbled more than 545 points in the final hours of the trading session to close at 25,052.83, taking its two-day decline past 1,300 points. The S&P 500  was also pulled lower in the downdraft, falling 57.31 points, or 2.14%, taking the broadest measure of U.S. stock prices below its 200-day moving average, a key measure that investors use to gauge market direction. The Nasdaq Composite index was also pummeled, falling more than 93 points to slide into what is known as correction territory, a condition traders use to describe market that has fallen more than 10% from a recent peak.

I had $VIX pegged for $30--almost got there. Nice spot to start a rally'...now that the crazies are out of the market with their moronic panic selling. Why don't they sell now, i mean did they go to college to get stupid, stupid?

— Jim Cramer (@jimcramer) October 11, 2018

U.S. Treasury bond yields also hit sessions lows as stock markets accelerated to the downside, as investors fled to safe-haven assets amid the global stock market rout. Benchmark 10-year notes were seen at 3.142% while 30-year bonds traded as low as 3.313% after an earlier auction of $15 billion in new paper that drew the biggest portion of foreign investors since the beginning of the year.

Energy stocks were the leading declines after a bigger-than-expected rise in domestic crude inventories, which is extending declines for global crude prices amid persistent concerns over the health of the world economy.

The Energy Information Administration said crude stocks rose by 6 million barrels in the week ending October 5, the third consecutive weekly advance and more than double the Street consensus of 2.6 million, to a weekly total of 409.5 million barrels. Stocks at the central distribution hub at Cushing, Oklahoma, which is used to price futures contracts, rose by 2.4 million barrels.

Brent crude contracts for December delivery, the global benchmark, were seen $2.78 lower from their Wednesday close in New York and changing hands at $80.27 per barrel while WTI contracts for November delivery, which are more tightly liked to U.S gas prices, closed $2.20 lower on the day at $70.97 per barrel.

The data, which followed a larger-than-expected buildup of 9.7 million barrels from the private American Petroleum Institute yesterday, is putting downward pressure on crude prices and sending U.S. energy stocks to the bottom of both the Dow Jones Industrial Average and the S&P 500 , along with comments from OPEC Secretary-General Mohammad Barkindo, who told an industry conference in London Thursday that "the market remains well supplied" and that "projections for 2019 clearly show a possible rebuild of stocks".

Energy stocks on the Dow were marked 3% lower following the EIA data, with Chevron (CVX) falling 3.2% to $118.7 and Exxon Mobil (XOM) sliding 2.51% to 81.98 and pulling the stock into negative territory for the year. The S&P 500 Energy Index was marked 2.7% to the downside, extending its third quarter decline to around 4%.