By Anora Mahmudova, MarketWatch

NEW YORK (MarketWatch) -- The U.S. stock market closed with sharp losses on Monday, after a much weaker-than-expected reading on manufacturing data as well as concerns over a slowdown in China, triggered the worst selloff in several months.

The S&P 500 and the Dow Jones Industrial Average ended the day with the steepest decline since June 20.

U.S. manufacturers expanded in January at the slowest rate in eight months as the pace of new orders sharply decelerated, according to the closely followed ISM index. The Institute for Supply Management index sank to 51.3% from 56.5% in December. That's the lowest level since last May. Economists surveyed by MarketWatch had expected the index to drop to 56%. Read: How reliable are ISM reports?

The S&P 500 index (SPX) closed down 40.70 points, or 2.3%, at 1,741.89, falling below the key level resistance level of 1,775. Market technicians watch this level closely, as closing below it would trigger heavy selling by algorithmic programs, which comprise about 40% of the market.

The Dow Jones Industrial Average (DJI) dropped 326.05 points, or 2.1%, to 15,372.80, falling below its 200-day moving average. The drop is the seventh triple-digit decline this year.

The Nasdaq Composite (RIXF) ended the day 106.92 points, or 2.6%, lower at 3,996.96, its worst one-day drop since June 1, 2012. The Russell 2000 (RUT) index of small-cap stocks finished the day 3.1% lower at 1,095.51 and is down 7.3% from its peak. Read the recap of our stock market live blog.

"The headline numbers from the ISM data were much weaker than expected and it would be interesting to see just how much of it is due to bad weather," said Quincy Krosby, market strategist at Prudential Financial.

"Investors will be watching the employment data on Friday very keenly, to see if there is a confirmation that we are somehow entering a soft patch. As the Fed continues with the tapering, the markets once again react to bad news negatively and are recalibrating valuations to economic data and earnings," Krosby said.

The main indexes ended January with the steepest losses in more than a year, as disappointing data from China -- which triggered selloffs in emerging-markets currencies over the past two weeks -- and worries over deflation in the euro zone forced investors to flee equity markets and seek safer assets.

The implied volatility as measured by the CBOE Vix index, which moves inversely to the S&P 500, jumped 14.6% to 21.09, a level not seen since Dec. 28 2012, when the markets confronted the fiscal cliff.

The 10-year Treasurys rallied, pushing yields to a fresh three-month low. Yields fell 7 basis points to 2.58%.

Less-than-stellar earnings results did little to alleviate fears among investors.

In other corporate news, shares of Jos. A. Bank Clothiers Inc. (JOSB) fell 5% after The Wall Street Journal reported Sunday that the company is in talks to buy fellow apparel retailer Eddie Bauer, citing sources. Jos. A. Bank and Men's Wearhouse Inc. (MW) have been locked in a monthslong battle to buy each other out. Shares in Men's Wearhouse slid 7.8%.

Herbalife Ltd. (HLF) saw a volatile trade after the company said it plans to offer $1 billion of convertible notes and use the proceeds to buy back shares. Shares closed 7.2% higher.

Ford Motor Co. (F) shares fell 2.7% after the car maker reported a 7% drop in January sales. General Motors Co. (GM.XX) reported that its U.S. sales in January fell 12%, more than expected by analysts. The stock fell 2.3%.

Pfizer Inc (PFE) shares pared earlier losses to gain 0.7%. The pharmaceutical giant said a trial for its advanced breast cancer treatment met its primary goal.

In other markets, the Nikkei Stock Average fell 2.4%, putting it in a technical correction as it closed at 14,619.13, which is just 10% off from a Dec. 30 high of 16,291.

European stocks markets moved lower on Monday, mirroring a negative mood in Asia, after Chinese manufacturing data added to fears about a slowdown in the world's second-largest economy.

More stories from MarketWatch:

6 easy ways to lose money in stocks

Treasurys rally on weak manufacturing data

'Stormy' January jobs report tough to figure

Subscribe to WSJ: http://online.wsj.com?mod=djnwires

Grafico Azioni Jos. A. Bank Clothiers (NASDAQ:JOSB)
Storico
Da Giu 2024 a Lug 2024 Clicca qui per i Grafici di Jos. A. Bank Clothiers
Grafico Azioni Jos. A. Bank Clothiers (NASDAQ:JOSB)
Storico
Da Lug 2023 a Lug 2024 Clicca qui per i Grafici di Jos. A. Bank Clothiers