The FTSE suffered a sharp drop in afternoon trading to close more than 3% in the red as concerns over EU debt and another Greece bomb attack rattled markets.
The FTSE opened more than 30 points up Thursday as investors were buoyed by Spanish plans to tackle its budget crisis, a host of strong trading updates and a rally on Wall St.
The FTSE edged higher while sterling fell from a 10-month high on the first day of the UK's new Coalition Government.
US stocks plunged to lows last seen in 1987 last night, amid speculation a trader entered a "b" for billion instead of an "m" for million when placing an order.
The FTSE 100 dived 1.52% or 80.94 points to 5,260.99 with banks dragging on the index after Moody's warned UK lenders are at risk of Greek contagion.
The FTSE was flat in early trading this morning at 5345.24 points as Europe's markets regained some composure after going into temporary freefall over the past two days.
The FTSE was off 0.83% at 5365.96 points this morning despite the largest miners regaining some of the ground they lost yesterday.
The FTSE 100 plunged 1.95% this afternoon as miners continued to weigh on the index following Australian plans to levy a 40% tax. The index fell 108.4 points to 5,444.89.
Dow Jones Indexes has launched four new indices within its Required Business Performance range, available as a basis for financial products.
Miners fell sharply this morning on news the Australian government plans to introduce a new 40% tax on resource projects from July 2012.