Share prices have dropped across Europe after a number of blasts rocked tube stations and buses across London.
The UK's benchmark FTSE 100 share index tumbled 105.92 points, or 3%, to 5,072. In France, Germany, Holland and Spain indexes all declined more than 2.5%.
The pound also dipped, while many investors sought safety in the Swiss franc and commodities such as gold. The price of crude oil dropped in London.
City firms including Deutsche Bank and the London Clearing House evacuated.
City-wide problem
Several people have been injured after explosions on the Underground network and a double-decker bus in London.
British Transport Police said some of the power surges had caused explosions.
A police spokesman said there were "quite a large number of casualties" at Aldgate Tube Station.
"There is always a bit of a scare when these kinds of incidents happen, especially after the Olympics announcement yesterday," one trader said.
"Everyone is already a bit worried today about the high oil price, there's a bit of uncertainty, the G8 is on today, so there's a bit of profit taking."
The shockwaves were felt as far away as South Africa, where shares dropped more than 1.8%.
"This is all on the back on the London underground incidents, and particularly the bus blast," said one Johannesburg trader.
"The market is getting pretty panicked. It's the uncertainty that is worrying everyone."
http://news.bbc.co.uk/1/hi/business/4659349.stm