Media playback is unsupported on your device Media caption Indonesian President Susilo Bambang Yudhoyono said food prices could lead to social unrest

World leaders have warned that rising food prices could lead to social unrest and even "economic war".

Indonesian President Susilo Bambang Yudhoyono said that with the world population rising, "the race for scarce resources" could lead to conflict.

And French President Nicolas Sarkozy called for regulation to rein in speculation and volatility in prices.

But business leaders at the World Economic Forum rejected calls for curbs on commodity speculation.

Future pressure

Mr Yudhoyono said the global population could rise from seven billion now to more than nine billion by 2045.

"Imagine the pressure on food, energy, water and resources," the Indonesian president said.

"The next economic war or conflict can be over the race for scarce resources , if we don't manage it together."

Nicolas Sarkozy, meanwhile, who holds the chair of both the G20 global economic forum and the G8 major economies, repeated his belief that regulation was needed.

Media playback is unsupported on your device Media caption Kamal Nath: "Fuel subsidies could hinder growth"

"Let those who buy big quantities of commodities commit to putting on deposit part of the financing for those commodities," he said.

EU internal markets commissioner Michel Barnier also criticised speculation in food commodities, calling it "scandalous".

However, Nils Anderson, boss of the shipping group AP Moller-Maersk, said it was not just speculators responsible for driving up commodity prices.

"You can say that if it is done by speculators, it is unfortunate. But it can also be done by governments trying to secure food supplies for their population. And it is really hard to criticise that," he said.