UK shares fell again on Friday, with mining stocks dragging the market lower as the prices of oil and commodities continued to tumble.
The FTSE 100 was down 124.9 points, or 2.1% at 5,793.3 points.
Overnight, BHP Billiton announced it was writing down the value of its US shale assets by $7.2bn amid the collapse in oil prices.
Meanwhile, US stocks were sharply lower after the drop in oil prices.
The Dow Jones Industrial Average finished down 321 points lower - 2.4% -15,987.26,
Phil Orlando, chief equity strategist at Federated Investors in New York, said: "Investors are scared to death."
After a brief recovery on Thursday, oil prices fell again to hit fresh 12-year lows. The price of Brent crude dropped to $29.01 a barrel at one point, before nudging back to $29.16 while US crude futures reached a low of $29.39 before edging up to $29.66.
The sell-off on the UK market followed another big fall in Chinese shares, with the Shanghai Composite dropping 3.5% on Friday.
In the FTSE 250, shares in Moneysupermarket fell 11% after investors were rattled by a larger-than-expected fall in sales in the company's insurance unit during the fourth quarter. Revenues in the insurance business were down 10% compared with a year earlier.
On the currency markets, the pound hit fresh five-and-a-half-year lows against the dollar after the release of weak UK construction data.
Official figures showed construction output in November fell by 0.5% compared with the month before, and was down 1.1% from a year earlier.
Sterling had already weakened earlier this week after industrial production figures showed a fall in output.
The pound slid to $1.4296, a new five and a half year low. Against the euro, sterling fell by more than one euro cent to €1.3057.