Alastair McCaig, market analyst at IG said trading screens were 'a sea of red' as talk of a Greek exit from the eurozone drives equity markets lower.
'We are now entering what could be the final chapter of the Greek saga, in which the indebted nation breaks free from the single currency and tries to go it alone.
'The rise of the anti-austerity Syriza party has sent shivers down the spine of dealers as they are well positioned for the election this month. A victory for the left-wing party does not automatically mean a Greek exit but traders will certainly see it that way.'
He added that the relentless battering of big oil stocks is only going to intensify as the world oil price approaches $50. Commodities stocks led the declines in both New York and London as the price of a barrel of Brent crude slipped below $54. It has more than halved from more than $115 a barrel in June.
Connor Campbell, financial analyst at Spreadex, said oil's decline into the new year had been prompted by a raft of weak manufacturing data last week.
He said: 'The black stuff is still looking abandoned and lost as 2015's trading begins in earnest, and continues to be a stain on the worldwide markets.'
In the US, the broader S&P 500 index shed 23.4 points to 2,034.9, and the tech-laden Nasdaq Composite fell 41.3 points to 4,685.5.
Shares in heavyweight FTSE 100 oil majors BP and Royal Dutch Shell fell sharply, down 3 per cent and more than 2 per cent respectively.
The euro meanwhile fell to nine-year lows as the spectre of a 'Grexit' rose again and expectations hardened that the European Central Bank will soon resort to cash injections to prop up the eurozone economy.