The FTSE 100 has finished an extremely rocky day of trading, down 3.5%, or 244 points, at 6,677.74.
Insurance group Prudential ended Thursday as the biggest blue chip faller, down 7% at £13.98, followed by mining giant Antofagasta, off 6.9% at 761.1p and industrial conglomerate Melrose whose shares shed 6.1% to end at 156p.
Only two companies rose on the FTSE 100 - both miners.
Randgold Resources rose 3% to £65.76 while Fresnillo added 1.4% to 785.8p.
Meanwhile, over in Europe...
The FTSE 100 is trading down 2.54% at 6,745.92.
The French CAC-40 is down 2.59% at 4,816.56 and in Germany, the DAX is down 2.84% at 10,883.23.
Her arrest - and possible extradition to the US for allegedly violating American sanctions against Iran - have raised concerns it could mar talks between the US and Chinese over trade just days after the two nations agreed a 90-day truce.
UK stock market closes down
The FTSE 100 has closed down 0.56% at 7,022.76 while the FTSE 250 finished 1.26% lower at 18,329.64.