NEW YORK (CNN/Money) - Stock prices tumbled yet again Monday as concerns about Citigroup's Enron connections and poor quarterly results from BellSouth added to the insecurity that has plagued investor confidence in recent weeks.

The Dow Jones industrial average tumbled 234.68 to 7,784.58; it was down more than 300 points earlier in the session. The average hit its lowest close since Oct. 8, 1998.

The Nasdaq composite index lost 36.50 to 1,282.65. The Standard & Poor's 500 index declined 27.90 to 819.85. Both indexes are trading at five-year lows.

Stock investors seemed to find little comfort in comments at a press conference by President Bush, meant to reassure investors that economic fundamentals are sound and that Congressional action to make corporations more accountable should help alleviate the selling.

"There's no safe haven, no place for investors to go," Gordon Charlop, a New York Stock Exchange member with Walter J. Dowd, told CNNfn's Street Sweep. "It's difficult to know when this thing is going to turn around."

After the close of trade, chipmaker Texas Instruments (TXN: Research, Estimates) said that it earned 6 cents per share in its second quarter, in line with estimates and better than the 3 cents it earned one year earlier. Chipmaker Altera (ALTR: Research, Estimates) also said it earned 6 cents per share, a penny above expectations but down from the 9 cents earned one year earlier.

Amazon.com, AT&T, Bristol-Myers Squibb, Duke Energy, Lam Research, Lucent Technologies, Openwave, SBC Communications and Tyco International are among the companies due to report quarterly results Tuesday:

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On Monday, shares of financial services company and Dow component Citigroup (C: down $3.93 to $28.11, Research, Estimates) traded sharply lower on amplified concerns about its exposure to Enron, the bankrupt energy trader, following several published reports.

Congressional investigators say Enron raised billions of dollars in cash from major banks in what essentially amounted to loans that it then hid as it struggled to stay afloat, according to the Washington Post. J.P. Morgan Chase (JPM: down $2.51 to $22.01, Research, Estimates) and Citigroup are among the banks that transferred more than $5 billion to Enron in the last year before its bankruptcy, using complex transactions that were labeled as energy trades, the paper alleged.

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"It's been a steady, slow grind down, the same thing we've been seeing for weeks," said Tim Heekin, head of stock trading at Thomas Weisel Partners. "You have the financials getting hit hard on the Enron stories and concerns about debt. Citigroup is heavily weighted and it's having an impact on the rest of the sector."

Regional telecom provider BellSouth (BLS: down $0.95 to $21.66, Research, Estimates) reported a weaker second-quarter profit than the year-earlier period that missed analysts' estimates, due to poor demand in the United States and Latin America. The news weakened other telecoms, including Dow component SBC Communications (SBC: down $0.96 to $23.00, Research, Estimates).

Another factor in market action: WorldCom (WCOM: Research, Estimates), the nation's No. 2 long-distance provider, filed for Chapter 11 protection late Sunday in the biggest bankruptcy in corporate history.

WorldCom's accounting problems have contributed to the plummeting of investor confidence that has shaken markets since the Enron scandal last fall. Last month, the company said it had improperly accounted for $3.9 billion in operating expenses. The company's shares continue to trade on the Nasdaq, where they're in danger of being delisted.

Also hurting technology, Sun Microsystems (SUNW: up $0.11 to $4.17, Research, Estimates) weakened after a Merrill Lynch note suggested that the No. 1 maker of Unix servers still may have downside risk. Other techs trading lower included Microsoft (MSFT: down $0.63 to $45.68, Research, Estimates) and Cisco Systems (CSCO: up $0.16 to $13.14, Research, Estimates).

"What we're seeing is typical of a market that is trying to make a bottom, but we're not necessarily there yet," said Peter Cardillo, director of research at Global Partners Securities.

On a positive note, diversified manufacturer 3M (MMM: up $1.85 to $110.85, Research, Estimates) posted a second-quarter profit of $1.36 a share, 2 cents above consensus and better than the $1.12 earned in the period a year earlier. The company also said it expects to top second-half forecasts.

Also providing some support, shares of consumer products maker Procter & Gamble (PG: up $1.46 to $79.29, Research, Estimates) rose after the Dow component said it will increase its stock repurchases in fiscal 2003 and that it remains confident about its business. In addition, UBS Warburg upgraded the stock to "strong buy" from "buy" within a broader upgrade of the household products makers.

Financial services company and Dow component American Express (AXP: up $0.14 to $29.11, Research, Estimates) reported second-quarter earnings of 51 cents a share, up from 15 cents a year earlier and 1 cent above analysts' forecast.

In a morning note, Lehman Brothers cut its year-end target for the Dow to 10,250 from 11,500 and its target for the Standard & Poor's 500 index to 1,075 from 1,200. The brokerage firm also instituted 2003 targets of 10,750 for the Dow and 1,125 for the S&P 500.

On Friday, the Dow lost almost 5 percent, while the Nasdaq lost nearly 3 percent, ending another week of extreme selling.

"It's still an underloved and oversold market as investors try to find their footing," said Bryan Piskorowski, market analyst at Prudential Financial. "All of the corporate governance concerns that have hit us for weeks are still there."

European markets weakened, while Asian-Pacific stocks finished mostly lower Monday.

Treasury prices rallied, pushing the 10-year note yield down to 4.45 percent. The dollar edged higher versus the euro and yen. Light crude oil futures lost $1.14 to $26.70 a barrel in New York. Gold dipped in U.S. trading.

Market breadth was negative. On the New York Stock Exchange, losers topped winners 5-to-2 as 2.15 billion shares traded. On the Nasdaq, decliners beat advancers 5-to-2 as 2.33 billion shares changed hands.