Jahangiri made the announcement on Monday night following an emergency meeting of the government's economic taskforce headed by Iranian President Hassan Rouhani.
The first vice president said that as of Tuesday the price of the dollar would be 42,000 Rials in both markets, and for all manner of activities.
He added that dollar sales at any other price would be considered "fraud".
On Sunday, Iran’s national currency the Rial plunged more than 6 percent against the US dollar in free market trade.
Commercial bankers previously linked the Rial’s slide partly to seasonal demand for US dollar, which rises around the end of the Persian year (March 21) when many Iranians travel abroad.
