Markets tumbled by around two per cent on Thursday morning as investors chose to take profits in the aftermath of comments from the head of the US Federal Reserve and a disappointing reading of manufacturing activity in China.The FTSE 100 had surged to a fresh 13-year high high of 6,840 the day before, its second-highest close in history, after Fed Chairman Ben Bernanke initiated with a dovish tone in a prepared speech to Congress on the central bank's easy-money policy. He initially said that the Fed would not scale back its asset purchase programme prematurely for risk of endangering the economic recovery and said that a highly accommodative stance will be appropriate "for a considerable time".However, when faced with questions from politicians, the Fed chief did hint that a tapering of quantitative easing measures could happen "in the next few meetings" if the Fed sees a sustained improvement in the economy.Markets have rallied strongly since the start of 2013 given aggressive monetary stimulus by countries across the world designed to kick start growth. As such, given the suggestion that the world's largest economy could soon start to reduce these unconventional measures, markets reacted with a sharp sell-off this morning. "The interesting thing on Thursday will be the reaction to the data on the markets," said Market Analyst Craig Erlam from Alpari ahead of US jobless claims figures out this afternoon."What we could now see, following Bernanke's comments yesterday, is positive data weighing on stocks and poor data contributing to the rally. If we continue to see an improvement in the weeks ahead, this could mark the end of the rally."In Asia overnight, markets suffered much steeper losses - with Japan's Nikkei diving a whopping 7.3% - as traders reacted to remarks from the Fed Chairman as well as some gloomy economic data from China.Factory activity growth in China moved backed into negative territory in May sparking worries over the recovery as the world's second-largest economy stagnates. The HSBC flash China manufacturing purchasing managers' index for the month of May unexpectedly fell to a seven-month low at 49.6 from the previous month's reading of 50.4. Analysts had forecast the index to rise to 50.5. Any reading below 50 indicates a contraction in the sector. FTSE 100: Banks and miners fall early onA fall in risk appetite this morning saw the banking and mining sectors decline sharply early on. RBS and Lloyds, which continue to be at the centre of reprivatisation speculation, were heavy fallers along with EVRAZ, Anglo American, Antofagasta and Glencore Xstrata.ARM Holdings was extending recent losses as Exane BNP Paribas joined the list of brokers to show caution on the chip designer stock following the group's investor day earlier this week. The broker downgraded its rating to 'neutral' today.Retail group Kingfisher was also under the weather after Nomura cut its recommendation to 'reduce', saying that the shares have gained too much recently "given weakness ahead".Drinks firm SABMiller was in the red despite increasing its full-year revenue from $31.4bn to $34.5bn in the year to end March.United Utilities was among the rare risers this morning after delivering a rise in full-year profit on the back of a strong operational performance.FTSE 250: Halfords plummets after dividend utCar and bike parts retailer Halfords sunk early on after the firm slashed its full-year dividend by nearly a quarter as profits dropped in the year to March 29th. The company said its performance reflected a "demanding trading environment".St James's Place was also a heavy faller after Lloyds cut its stake in the wealth manager for the second time in three months, placing 77m ordinary shares (representing 15% of the company) at a 9.3% discount to last night's closing price.FTSE 100 - RisersUnited Utilities Group (UU.) 790.00p +1.09%Associated British Foods (ABF) 1,952.00p +0.57%Sainsbury (J) (SBRY) 383.90p +0.50%FTSE 100 - FallersARM Holdings (ARM) 990.00p -5.71%Evraz (EVR) 148.80p -4.25%Aggreko (AGK) 1,784.00p -4.19%GKN (GKN) 299.20p -4.07%Antofagasta (ANTO) 962.50p -3.94%Anglo American (AAL) 1,589.00p -3.90%Barclays (BARC) 321.00p -3.85%Royal Bank of Scotland Group (RBS) 336.20p -3.83%Standard Chartered (STAN) 1,557.50p -3.62%Hargreaves Lansdown (HL.) 998.00p -3.39%FTSE 250 - RisersBooker Group (BOK) 131.20p +1.16%PayPoint (PAY) 900.00p +1.12%Lonmin (LMI) 272.90p +0.92%Petropavlovsk (POG) 127.80p +0.63%Brewin Dolphin Holdings (BRW) 211.30p +0.38%Drax Group (DRX) 593.00p +0.34%BH Global Ltd. USD Shares (BHGU) 12.34 +0.24%Centamin (DI) (CEY) 39.40p +0.13%BTG (BTG) 338.70p +0.09%FTSE 250 - FallersHalfords Group (HFD) 334.70p -15.54%Salamander Energy (SMDR) 176.50p -13.90%St James's Place (STJ) 575.00p -10.16%Ferrexpo (FXPO) 178.40p -7.23%Man Group (EMG) 125.00p -6.37%888 Holdings (888) 164.20p -6.01%New World Resources A Shares (NWR) 108.50p -5.65%International Personal Finance (IPF) 523.00p -5.42%AZ Electronic Materials SA (DI) (AZEM) 318.60p -5.29%Dialight (DIA) 1,285.00p -5.24%