US stocks tumbled on Friday after investors were unnerved by disappointing results from Coca-Cola Co and Microsoft Corp and fretted about possible attacks at next week's Democratic National Convention.
The technology-heavy Nasdaq Composite index notched a fresh low for the year.
The blue-chip Dow closed below the psychologically key 10,000 level for the first time in two months and declined for the fifth week in a row.
The Standard & Poor's 500 index logged its sixth consecutive week of losses.
"Microsoft set the pace for the start of the day, but it's the Friday ahead of the Democratic convention," David Hegarty, head of equity trading for Commerzbank Securities, said. "We're continually seeing these investigations into terror-related warnings."
US Homeland Security Secretary Tom Ridge earlier this month warned that Osama bin Laden's al Qaeda militant group may attack the United States in a bid to disrupt the November election. And on Friday the FBI said it was investigating "unconfirmed information" of a possible attack on media vehicles during the convention, which begins in Boston on Monday.
The Dow Jones industrial average ended down 88.11 points, or 0.88 percent, at 9,962.36, while the Nasdaq closed off 39.97 points, or 2.12 percent, at 1,849.28. The S&P 500 Index ended down 10.64 points, or 0.97 percent, at 1,086.20.
For the week, the Dow average was down 1.75 percent, while the Nasdaq fell 1.8 percent and the broad S&P 500 was off 1.4 percent. The Dow is down more than 4 percent for the year, the Nasdaq down 7 percent and the S&P 500 is down 2 percent.
A series of earnings reports and outlooks from major companies that failed to beat Wall Street's expectations or even missed them has investors worried that profit growth will slow in the rest of the year, traders said.
Microsoft, the world's second-largest company by market value, on Thursday said its profit for the year will be weaker than expected as investment income slows as a result of its huge $32 billion payout to shareholders.
Coca-Cola, reported on Thursday a 16 percent jump in quarterly net profit, but provided volume figures that fell below expectations.
Sanford Bernstein said on Friday it cut its rating on the stock to "market perform" from "outperform."
Web retailer Amazon.com Inc posted quarterly profits that were a penny short of Wall Street's expectations and its forecast for the third quarter also lagged Wall Street expectations.
Trading was active, with 1.3 billion shares changing hands on the New York Stock Exchange, just shy the 1.4 billion daily average for last year.
About 1.7 billion shares were traded on Nasdaq, below the 1.8 billion daily average last year.
Coca-Cola dropped $3.80, or 7.8 percent, to $45.17, making it the biggest drag on the Dow and the S&P 500. Microsoft fell 97 cents, or 3 percent, to $28.03, making it the biggest weight on the Nasdaq. Amazon's stock fell $5.84, or 12.8 percent, to $39.98 on Nasdaq.
Champion Enterprises Inc, the top US builder of manufactured homes, was the largest percent gainer on the NYSE after posting a sharply higher quarterly profit. The stock ended up 1.88, or 25 percent, at $9.55.
So far in July, the S&P is down nearly 5 percent. If the market stays flat market next week, the loss for the month will be the largest since a 6 percent decline in December 2002.