Asian shares, the euro, commodities and the Australian dollar all fell Thursday as fears that Europe's debt crisis could unleash financial chaos prompted investors to shed riskier assets in favor of the relative safety of the dollar.

U.S. stock futures also fell, retreating from a Wall Street rebound on Wednesday, as leaders of the world's biggest economies began arriving in France for a G20 summit that will be dominated by the threat of a Greek exit from the euro zone.

Asian stocks dropped 1.5 percent, while oil, copper and the commodity-linked Aussie fell around 1 percent and credit markets weakened.

The leaders of France and Germany, angered at Greece's shock move to call a referendum on its latest bailout plan negotiated last week, told Prime Minister George Papandreou Wednesday that Athens would not receive another cent in EU aid until it decides whether it wants to stay in the euro zone.

It's clearly a worse situation as it is putting other euro zone members in a corner, said Jeremy Friesen, a commodity strategist at Societe Generale in Hong Kong.

If Greek voters reject the 130 billion euro bailout package, which requires harsh austerity measures, it could lead to a disorderly default, with the fallout affecting European banks and rippling across the global financial system.

MSCI's broadest index of Asia Pacific shares outside Japan <.MIAPJ0000PUS> fell 1.5 percent, while S&P 500 futures traded in Asia lost 1.3 percent. Wall Street shares had gained more than 1.5 percent on Wednesday.

Tokyo's financial markets were closed for a public holiday.

ECB IN FOCUS

As well as watching events at the G20 summit in Cannes, investors were also focused on Frankfurt, where the European Central Bank was holding its first policy meeting under new President Mario Draghi.

Many analysts see the ECB as the only institution with the firepower to calm tensions, and the key question after the meeting -- at which no change in interest rates is expected -- will be whether it will increase its purchases of bonds issued by debt-ridden euro zone states.

On Wednesday the U.S. Federal Reserve offered no new stimulus, but said it was mulling the possibility of buying more mortgage debt to spur a struggling recovery.

The euro fell 0.5 percent to around $1.3680 as investors took sanctuary in the dollar, which rose by a similar margin against a basket of six major currencies .DXY.

The pullback from risk also knocked oil lower, with U.S. crude down more than 1 percent at $91.46 a barrel and Brent crude off 0.6 percent at $108.69.

Copper fell 0.9 percent on the London Metal Exchange to below $8,000 a tonne.

The Australian dollar, seen as a risk currency because it is heavily influenced by demand for Australia's natural resources, fell 1 percent to around $1.0230.

In Asian credit markets there was a modest widening of spreads on the iTraxx Asia ex-Japan investment grade index, which can be used as a gauge of risk appetite.

Gold, in recent months has largely flipped from a negative to a positive correlation with riskier commodities as safe-haven seekers favor the dollar. The yellow metal fell 0.7 percent to around $1,726 an ounce.

(Editing by Ramya Venugopal)