NEW YORK (Reuters) - The Dow industrials suffered its worst slide since July on Friday on concerns that the economic recovery won't be robust enough to sustain the seven-month stock rally, while financials sank on renewed worries about Citigroup's balance sheet.

Investors unloaded shares across the board on the day that marked the end of the fiscal year for many mutual funds, putting the S&P 500 on the brink of a correction.

Wall Street's favorite measure of investor fear, the CBOE Volatility Index, soared 24 percent -- its biggest one-day percentage gain since October 2008 -- and the Dow had its worst day since July.

Analysts said there were doubts that the recovery would be strong enough to justify higher stock prices a day after government data showed the economy returned to growth in the third quarter.

"There's still some systemic risk to the environment," said Anthony Conroy, head trader for BNY ConvergEx, an affiliate of the Bank of New York, in New York.

"You need growth, you need a healthy financial system to have a healthy economy. There are questions out there about how things go from here. Right now the government is fueling the system with cash. That can't last forever."

The Dow Jones industrial average slid 249.85 points, or 2.51 percent, to end at 9,712.73. The Standard & Poor's 500 Index tumbled 29.92 points, or 2.81 percent, to 1,036.19. The Nasdaq Composite Index dropped 52.44 points, or 2.50 percent, to close at 2,045.11.

Both the S&P 500 and the Nasdaq snapped seven straight months of gains.