Mobile phone text messages containing the word "dollar" and a website showing real-time exchange rates were blocked on Tuesday in Iran, as authorities struggled to reverse a dramatic slide in the value of the Iranian rial.
Some Iranian media outlets noticed that SMS, or text messages, containing the word "dollar" – in either English or Farsi – were not being sent over the cellular network.
Foreign journalists in Tehran, including AFP, verified the text-message block, which also affected the Farsi word for "foreign exchange.” The word "euro" and currency symbols were transmitted freely.
The ISNA news agency questioned Iran's two cell network operators, MCI and Irancell, about the block. Both asserted that they were not filtering the messages.
The text message block added to the inaccessibility over the past week of the mesghal.ir website that shows the rial's value against world currencies.
The rial has lost more than a third of its value against the dollar in the past three months, much of it in an accelerated slide observed in the first days of 2012 after the United States enacted a law targeting Iran's central bank.
On Tuesday, the rial was fetching 17,230 against the dollar on the open market. That was close to the record low of 17,800 it hit on January 2.
Iranian officials insist the rial's decline has nothing to do directly with the Western sanctions, the toughest of which have yet to come into effect.
But some said Iranian residents were psychologically spooked by the sanctions squeeze and the prospect that the situation would worsen still.
The United States and its Western allies have been imposing sanction after sanction to pressure Tehran over its nuclear program, which they allege is being used to research the development of atomic weapons.
Iran denies that and has warned it could close the strategic Strait of Hormuz in the southern Gulf to the 14 or so tankers that each day carry Middle Eastern oil to the world if the sanctions halt its petroleum exports.