BANGKOK, Thailand - Asian stock markets tumbled Friday as investors dumped riskier assets amid fears the U.S. is heading back into recession and Europe's debt crisis is worsening.

The sell-off in Asia followed the biggest one-day points decline on Wall Street since the 2008 financial crisis.

Japan's Nikkei 225 stock average slid 3.4 per cent to 9,335.26 and Hong Kong's Hang Seng shed 4.1 per cent to 20,989.28.

Australia's S&P/ASX 200 was off 4 per cent at 4,107.20, Taiwan's Taiex sank 4.2 per cent to 7,967.38 and Seoul's Kospi dropped 2.8 per cent to 1,961.79.

Growing fear about the weakening U.S. economy was joined by concern in Europe that the troubled economies of Italy and Spain might need help from the European Union.

But some analysts said the sell-off was not a repeat of 2008 when a banking and credit crisis sent markets into a prolonged tailspin.

Traders also unloaded stocks before Friday's release of the U.S. government's unemployment report for July, which is expected to show weak job growth and perhaps a rise in the unemployment rate, which is 9.2 per cent.

For the day, the Dow closed down 512.76 points, at 11,383.68. It was the steepest point decline since Dec. 1, 2008.

Thursday's decline was the ninth-worst by points for the Dow. In percentage terms, the decline of 4.3 per cent does not rank among the worst. On Black Monday in 1987, for example, the Dow fell 22 per cent.

Benchmark oil for September delivery was down $1.16 at $85.47 a barrel in electronic trading on the New York Mercantile Exchange. The contract fell $5.30, or 5.8 per cent, to settle at $86.63 on Thursday.