Global stock markets and the euro have soared after the biggest international intervention since the 2008 banking crisis was agreed at all night talks in Brussels.
European nations and the IMF set up a nearly one-trillion-dollar war chest to support the euro while central banks around the world joined the battle to lift market fears of a growing debt crisis.
The euro shot up above 1.30 dollars from 1.2755 on Friday. The London stock market surged more than five percent in morning trade and Tokyo closed up 1.6 percent.
European leaders said they were determined to defend the euro and struggling governments, but many analysts were still asking however whether it would be enough.
"We are protecting our currency in an extraordinary situation," said Chancellor Angela Merkel of Germany, Europe's number one economy and the biggest backer of the fund set up to save Greece, which set off the debt crisis.
"I hope that this will mean the end of the battle" against speculators, Spain's Foreign Minister Miguel Angel Moratinos said in Brussels.
"This package serves to strengthen and protect the common currency," added Merkel, who held emergency talks with US President Barack Obama and other world leaders before the accord.
But she added a call for debt-stricken European nations to take action. "We must attack the problem at its roots," she said. "In this process, budget consolidation in all member states becomes extraordinarily important."
European Union finance ministers agreed the 750 billion euro (975 billion dollar) package of loan guarantees and credits in talks lasting more than 11 hours that ended early Monday.
Some €440 billion would come from eurozone nations and 60 billion euros from the European Commission. Another €250 billion euros would come from the International Monetary Fund.
"EU finance ministers have rushed to 'shock and awe' the markets by formulating a 'crisis mechanism' package with the IMF," said Mitul Kotecha, a Credit Agricole analyst in London.
Europe is aiming to leverage vast borrowings to prop up nations the way governments kept banks alive during the 2008 global financial crisis -- keeping interest rates down.
The European Central Bank (ECB) joined the US Federal Reserve and the central banks of Britain, Canada and Switzerland in coordinated moves, mainly through dollar swaps, aimed at nudging global money, debt and currency markets forward.
The ECB said the Bank of Japan would soon begin considering such measures as well.
It cited "exceptional circumstances," with central banks to intervene to ensure that dollar shortages do not occur.
South Korea, which will chair a Group of 20 summit in November, released a statement saying members were "strongly committed" to working together to maintain global financial stability.
The package was described as "far-reaching" by IMF managing director Dominique Strauss-Kahn.
The ECB had been pressed to implement a so-called "nuclear" option under which it would buy euro countries' bonds or accept toxic eurozone government debt as collateral.
Pressure mounted on the German chancellor after her governing coalition lost its majority in the German upper house, as angry voters punished the government for agreeing a 110-billion-euro international bailout for Greece.
Germany's wheelchair-bound Wolfgang Schaeuble monitored the talks from a Brussels hospital bed after suffering an allergic reaction to new medication.
With markets harbouring doubts about debt mountains and deficits in Portugal, Spain and Italy -- and even France and Britain -- the new package goes far beyond the system put in place for Greece, which won loan commitments over three years in exchange for radical spending cuts and economic reforms.
Spain and Portugal committed to speed up the reduction of their public deficits in 2010 and 2011.
But the talks were marked by dispute as Britain's Labour government refused to provide direct guarantees for the euro, amid power-sharing talks at home that could deliver a new right wing Conservative-led government within days.
"It is difficult to tell now whether the measures agreed will be sufficient to calm the markets, thus stabilising the euro," Commerzbank analysts said in a report.
"While contagion effects will be largely prevented thanks to the ECB’s bond purchases, the euro might well remain under pressure. The volume of the aid programme is likely to be much smaller than the official figures suggest."
Peter Morici, an economy professor at the University of Maryland in Washington DC, said: "More budget crises will follow, if not in Greece then in Portugal, Spain, or perhaps Ireland or Italy, because the euro is simply not backed by a strong central government."