When angry motorists torched petrol stations as Tehran introduced rationing last month, Iran's opponents scented success. Israeli prime minister Ehud Olmert said it showed "economic sanctions are working increasingly well".

But after three weeks of rationing, riots have given way to grumbling. Tehran's streets are less congested, its air more breathable, and the government says it is on target to reduce a bill for imported petrol that was due to hit $7bn this year.