US stocks plunged on the opening Monday, triggering the third halt in trading in the last six market sessions as investors feared the Federal Reserve's latest cut in interest rates won't be enough to counter an economic slowdown caused by the spread of the coronavirus.

Dow Jones Industrial Average fell 2,250.4 points, or 9.7 percent. The S&P 500 lost 220.55 points, or 8.1 percent. The Nasdaq Composite fell 482.15 points, or 6.12 percent.

The market edged slightly lower when trading resumed after a 15-minute halt.

In response, investors sought safety in US government bonds as concern about global growth prospects grew.

The yield on the benchmark 10-year US Treasury note fell to 0.762 percent from 0.946 percent at Friday's market close as the price edged up. Bond yield and price move in opposite directions.

In emergency action Sunday, the US Federal Reserve cut interest rates to 0 – 0.25 percent. The Central Bank also announced a new $700 billion round of quantitative easing, or asset purchases intended to pump new funds into the money supply.

"The Federal Reserve is prepared to use its full range of tools to support the flow of credit to households and businesses and thereby promote its maximum employment and price stability goals," the Fed said in a statement.

"To support the smooth functioning of markets for Treasury securities that are central to the flow of credit to households and businesses, over coming months, the (Federal Open Market Committee) will increase its holdings of Treasury securities by at least $500 billion and its holdings of agency mortgage-backed securities by at least $200 billion."

Some analysts fear the Fed has launched all its arrows in a three-week span and therefore can't use interest rate cuts in the future to stimulate the economy.

At a news conference after announcing the rate cut Sunday, Fed Chairman Jerome Powell said:

"We will maintain the rate at this level until we're confident that the economy has weathered recent events and is on track to achieve our maximum employment and price stability goals," Powell said. "That's the test. We're going to be watching, and willing to be patient, certainly," he added.

JPMorgan Chase said last week's stock sell-off was overdone, but implied a 65 to 75 percent of recession in the next 12 months. A recession is defined as two consecutive quarters of negative growth.

"The market has gone ahead and priced in too severe of an adverse scenario, assuming we get timely and strong counter-policy response and a Covid-19 outbreak that peaks in the coming weeks," Dubravko Lakos-Bujas, JPMorgan's chief equity strategist, said in a research note to investors.

"The speed and intensity of the sell-off has shaken investor confidence with many now modeling recession scenarios even though there is still significant lack of clarity on the actual fundamental impact."

The market rout in the last two weeks has wiped out the S&P 500's gains of the last two years. But there may be a rebound ahead because "equal or worse single day sell-offs were followed by median forward returns of +4 percent and +17 percent over the subsequent 1-week and 12-month periods, respectively," he said.

Brent crude oil, a global benchmark, fell 10.10 percent in early trading to $30.44 a barrel — more than 50 percent lower since the start of the year. Oil is seen as a gauge of future economic activity. The continued slide suggests investors anticipate a worldwide economic slowdown.

Copper futures were down 4.34 percent in early trading. Copper is used extensively in electronic and consumer products as well as in construction. Like oil, the drop in copper prices suggests investors see economic stagnation ahead.