NEW YORK (AP) — Stocks plummeted Monday morning on Wall Street on a combination of coronavirus fears and plunging oil prices, triggering a brief, automatic halt in trading to let investors catch their breath.

The price of oil sank 20% after Russia refused to roll back production in response to falling prices and Saudi Arabia signaled that it will ramp up its output.

While low oil prices can eventually translate into cheaper gasoline, they are wreaking havoc on already struggling energy companies and countries that depend on oil, including the No. 1 producer, the United States.

The war between the giant oil producers came just as Italy heads for a huge hit to its economy as it enforces a lockdown on 16 million people in the northern part of the country, the heart of its manufacturing and financial industries. The turmoil is expected to push Italy into recession and weigh on the European economy.

The carnage in stock and bond trading was nearly as breathtaking as in oil markets.

In the United States, the S&P 500 plunged as much as 7.4% in the first few minutes of trading, and losses were so sharp that trading was temporarily halted. Stocks trimmed their losses following the halt, and the index was down 6%, as of 11:12 a.m. Eastern time.

The Dow Jones Industrial Average lost 1,619 points, or 6.2%, to 24,261 after briefly being down more than 2,000. The Nasdaq gave up 5.6%.

The carnage in the energy sector was particularly arresting. Marathon Oil, Apache Corp. and Diamondback Energy each sank more than 40%. Exxon Mobil and Chevron were on track for their worst days since 2008.

“The path of least resistance is still down,” said Liz Ann Sonders, chief investment strategist at Charles Schwab.

Treasury yields careened to more record lows as investors dove into anything that seems safe, even if it pays closer to nothing each day. Traders are increasing bets that the Federal Reserve will cut interest rates back to zero to do what it can to help the virus-weakened economy, perhaps as soon as next week.

All the drops are the result of fear of the unknown. As COVID-19 spreads around the world, many investors feel helpless in trying to estimate how much it will hurt the economy and corporate profits, and the easiest response to such uncertainty may be to get out. After initially taking an optimistic view on the virus — hoping that it would remain mostly in China and cause just a short-term disruption — investors are realizing they likely woefully underestimated it.

The virus has infected more than 110,000 worldwide, and Italy on Sunday followed China’s lead in quarantining a big swath of its country in hopes of corralling the spread. That sparked more fears, as quarantines would snarl supply chains for companies even more than they already have.

The new coronavirus is now spreading on every continent except Antarctica and hurting consumer spending, industrial production, and travel.

The S&P 500 has lost 17% since setting a record last month. If it hits a 20% drop, it would mean the death of what’s become the longest-running bull market for U.S. stocks in history. Monday actually marks the 11th anniversary of the market hitting bottom after the 2008 financial crisis.

A measure of fear in the U.S. stock market soared to its highest level since 2008. That means traders are more worried about upcoming swings in the S&P 500 now than they were during the European debt crisis, the U.S.-China trade war or at the height of recession worries after the Federal Reserve raised rates four times in 2018.

The circuit breaker tripped in the U.S. stock market is meant to slow things down and give investors a chance to breathe before trading more.

The yield on the 10-year Treasury note plunged to 0.54%, down sharply from 0.70% late Friday. Early last week, it had never been below 1%.

Short-term yields sank as traders placed increasing bets that the Federal Reserve will cut rates deeper to do what it can to help the economy. The two-year Treasury yield, which moves more on expectations of Fed action, fell to 0.33% from 0.46%.

The Federal Reserve and other central banks around the world have provided the ultimate backstop in the past during this bull market, supporting markets with rate cuts and other measures of stimulus. But doubts are rising about how effective lower rates can be this time. They can encourage people and companies to borrow, but they can't restart factories, restaurants or theme parks shut down because people are quarantined.

Many analysts and professional investors say they expect big swings to continue to dominate the market as long as the number of new virus cases is accelerating.

Brent crude, the international standard, lost $8.60, or 19%, to $36.67 per barrel. Benchmark U.S. crude fell $7.16 to $34.12.

Investors were already knocking oil down because of worries that a virus-weakened global economy will burn less fuel. But concerns about supply dropped the latest scythe on the market Monday. Reports that Saudi Arabia may increase production of oil to grab market share led to worries that the world may soon be awash in too much oil.

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AP Business Writer Damian J. Troise contributed.