The Iranian rial has lost almost two-thirds of its value since the start of the year, and 20 percent in just two days since the weekend, hitting a record-low of 119,000 to the dollar.

Many lay the blame on the imminent reimposition of US sanctions on August 6 following US President Donald Trump's decision to pull out of the historic nuclear accord, with Iranians rushing to store their savings in dollars.

The central bank issued a statement on Monday that trod a familiar line, blaming "the enemies' conspiracies" for the rial's sudden decline.

This may not be purely paranoid fantasy. The US and its Gulf Arab allies are engaged in a "maximum pressure campaign" against the Iranian government, and there have been rumours that the United Arab Emirates has been curbing the physical supply of dollars to Iran, helping drive up prices.

But others say outside pressure is only effective because Iran's economy is so corrupt and poorly managed.

Belatedly, the authorities appear to be waking up to the crisis. This weekend, the judiciary announced 60 people had been arrested for fraud and trying to undermine the banking system, with more to come.

Spokesman Gholam Hossein Mohseni-Ejeie said several had direct ties to the government, allowing them, for example, to illegally import luxury cars, and could face the death penalty on Iran's infamous charge of "corruption on Earth".