Gold price declines to two-year low
Gold has fallen to its lowest level in two years, while wider commodity prices have also declined following disappointing Chinese economic data.
The price of the precious metal was down 9.2% to $1,395 an ounce.
Meanwhile, oil prices fell to four-month lows, with Brent crude down $2.29 to $100.75 a barrel, and the main US share index, the Dow Jones, ended down 1.8%.
This was the Dow's biggest fall since November.
Analysts said that the explosions at the Boston Marathon also contributed to the fall in share prices.
The price of copper and aluminium were also sharply lower.
Copper fell to its lowest level in a year and a half at $7,085 a tonne, and aluminium sank to a three-and-a-half year low.
Analysts said a key factor in gold's fall was the expectation that the US central bank, the Federal Reserve, will tighten monetary policy by stopping its quantitative easing (QE) programme.
This means that the rate of US inflation is likely to fall, meaning investors have less reason to hold gold to avoid a corresponding decline in the value of cash investments.
Cyprus's announcement last week that it was planning to sell most of its gold reserves has also had an impact on the fall in the price of gold.
Some analysts fear that other weak eurozone economies, such as Italy and Spain, will follow Cyprus's lead and sell some of their gold stocks, adding further supply to weakening demand.
Dominic Schnider, an analyst at UBS Wealth Management, said it might not have been the eurozone that triggered the mass flight out of gold: "What we now see is panic selling, perhaps triggered by the Fed's stimulus view. The Fed has given the signal that there's a possibility to reduce QE and that took a lot of trust out of gold.
"And people recognise that an environment where you have no inflation is a powerful driver to get out of the metal."
The wider commodity and share declines follow after China said overnight that its economy expanded by 7.7% in the first quarter of 2013, lower than forecasts and below the pace of growth of recent years.
The price of gold has had a remarkable run in recent years, hitting a record high of $1,800.
Another drag on prices has come from India, the world's biggest buyer of gold bullion, which introduced a 50% import tax that has triggered a 24% fall in the amount of gold brought into the country in the first quarter of this year.
Mohit Kamboj, president of the Bombay Bullion Association, suggested prices may have further to fall: "With more and more countries reducing stocks, the future of gold seems bleak."
The fall means Cyprus is likely to raise less than the 400m euros ($525m) it hoped for when it announced it was selling the bulk of its gold reserve.
Gold mining company shares fell sharply as a result, with Fresnillo ending down 15%, and Randgold dropping 8.3%.
David Govett, head of precious metals at Marex Spectron in London, said there was a mass flight out of gold: "We have seen massive liquidation from all quarters... This is a market that has only got one thing on its mind... get me out."