The Greek government said it would hold a general election on May 6, with opinion polls showing support for the mainstream pro-austerity parties is too weak to allow them to form a government.
"Spain is a big focus right now and even Greece will be coming back into the picture as it looks for another tranche of aid, so this euro zone debt tragedy is not going away, but seems to be getting worse," said Daniel Hwang, senior currency strategist at Forex.com in New York.
Interest rates on 10-year Spanish bonds hit 6% for the first time since January, when Europe's leaders were battling to agree a bailout deal for Greece and secure the future of the euro zone. Shares in Madrid dropped by almost 3% to hit their lowest level since March 2009.
In Italy, share prices slumped by 5% on rumours that the government was preparing to downgrade its growth forecasts, and trading in the shares of several of its banks was suspended after they fell sharply.
Shares were also much lower on Wall Street, where the fallout from Europe exacerbated fears that the US recovery is petering out. Disappointment at last week's unemployment figures had already been weighing heavily on investor confidence.
The markets closed in New York with Wall Street completing a fifth successive day of decline, with the Dow Jones having lost 213 points. In London, the FTSE 100 closed down 128 points, at 5,595.55. Oil prices also fell sharply amid concerns about the prospects for growth on both sides of the Atlantic and in Asia, with the price of a barrel of crude falling by more than $2.
In contrast, safe haven assets such as gold, the U.S. dollar and bonds in the U.S., Germany and Britain were all in demand. "The market went up on a wave of liquidity-induced euphoria, and as usual overshot. Now the clever boys have decided to get out," said Charles Dumas of Lombard Street Research.
Europe's politicians had hoped that Greece's second bailout, and a battery of emergency measures unleashed by the European Central Bank, including its long-term "repo" operation, which offered cheap money to troubled banks, would draw a line under months of economic chaos. But Erik Britton, of City consultancy Fathom, said: "The LTRO [long term refinancing operation] and all those things, all it's done is bought a bit of time, but it hasn't addressed the structural problems, even slightly, even for Greece."
He predicted that the ECB could be forced to take fresh rescue measures in the next few weeks to prevent strains in Europe's banking sector from turning into a credit crunch, while in the longer term several more countries – including Spain and Italy – would eventually be forced to write off a proportion of their debts before the crisis is over.
The euro came under pressure on the foreign exchange markets as the mood darkened on Tuesday, losing 0.2% against the dollar, to $1.3080, and more than 1% against the yen. David Song, Currency Analyst at DailyFX, said: "The single currency is likely to face additional headwinds over the near term as the region continues to face a risk for a prolonged recession."
Spain's prime minister, Mariano Rajoy, speaking in the country's senate, warned that his government must stick with its austerity plans, saying: "There's no doubt that much of Spain's future is at stake and also economic growth and the creation of jobs over the coming years."
But the central bank governor, Miguel Ángel Fernández Ordóñez, added to the mood of anxiety by warning that unless the economy improves, the country's struggling banks will need a new government bailout. Successive waves of austerity measures have already driven Spanish unemployment to 23%. Some 50% of young people are out of work.
Jane Foley, currency strategist at Rabobank, said: "The Spanish government appears to be losing the battle to restore budgetary credibility while each additional austerity measure serves to feed the recessionary backdrop."
In London, Barclays shares fell by 6% to 206p and were the second-biggest faller in the FTSE100 amid fears about its troubled Spanish operation. In February Barclays borrowed €6 billion from the ECB's cheap loans scheme to pour into its Spanish operations.
The fresh bout of turbulence comes as the world's finance ministers and central bank governors prepare to fly to Washington next week for the half-yearly meeting of the International Monetary Fund. Following the measures taken by the ECB, the fund had been hopeful that the talks would be less fraught than those last autumn, when Europe's leaders were told to get to grips with their problems.
Christine Lagarde, the IMF's managing director, will almost certainly use the renewed crisis in the single currency zone to seek support for an increase in the fund's resources. But several countries, including the U.K., have signaled that they would be reluctant to contribute significant new funds to the IMF unless they can be convinced eurozone leaders have done everything possible to tackle sovereign debt.
Intellpuke: You can read this article by the Observer's Economics Editor Heather Stewart, Guardian Economics Editor Larry Elliott and Correspondent Miles Tremlett, reporting from Madrid, Spain, in context here: www.guardian.co.uk/world/2012/apr/10/european-stock-market-panic-selling