Global shares post losses
US stocks slid in a volatile session, with the Nasdaq closing below the 4,000 mark for the first time since early February.
Selling accelerated late in the afternoon, with the biotech and other momentum stocks again leading the Nasdaq sharply lower. JPMorgan's disappointing earnings also gave investors a reason to sell some bank stocks.
For the week, the S&P 500 fell 2.6 percent and the Nasdaq lost 3.1 percent, the biggest weekly decline for both indexes since June 2012.
The Dow Jones industrial average .DJI fell 143.47 points or 0.89 percent, to end at 16,026.75. The S&P 500 .SPX lost 17.39 points or 0.95 percent, to finish at 1,815.69. The Nasdaq Composite .IXIC dropped 54.372 points or 1.34 percent, to close at 3,999.734.
The Nasdaq Composite fell through 4,000 for the first time since early February and many one-time market darlings are now down substantially from records reached only six or seven weeks ago.
JPMorgan Chase & Co (JPM.N) shares fell 3.7 percent to close at $55.30. The stock was the biggest drag on the S&P 500 after the bank reported a far weaker-than-expected quarterly profit as revenue from securities trading fell.
The S&P financial index .SPSY dropped 1.2 percent. It was the S&P 500's worst-performing sector.
The Nasdaq biotech index .NBI fell 2.8 percent after rising as much as 1 percent earlier. The Global X social media index (SOCL.O), which includes Facebook (FB.O) and LinkedIn (LNKD.N), slid 2.3 percent. Facebook shares fell 1.1 percent to $58.53. LinkedIn shares lost 2.5 percent to end at $165.78.
Trading volume was around 7.3 billion shares on US exchanges, above the 6.9 billion average so far this month, according to data from BATS Global Markets.
In Europe, shares slid today to leave them set for their first weekly loss in a month, tracking steep falls in Asian and US stocks as equities came under pressure globally.
The pan-European FTSEurofirst 300 fell 1.4 percent to 1,312.37, with no sectors in positive territory.
Meanwhile, Japanese shares tumbled to six-month lows and posted their biggest weekly fall since the March 2011 tsunami and nuclear disaster after a rout in US tech shares spurred selling by momentum players.
The Nikkei fell 2.4 percent on the day to 13,960.05, the lowest finish since Oct. 8 and down 7.3 percent on the week.
It was the biggest weekly fall since the week following the earthquake in March 2011, when the Nikkei fell 10.2 percent.