According to foreign exchange website Bonbast.com, the rial fell to 112,000 on the unofficial market, down from 97,500 just 24 hours earlier.
Since April, the rial’s value has halved because of a weak economy, financial difficulties at local banks and intense demand for dollars among the Iranian people who fear the effects of the sanctions after the US pulled out of the Iran nuclear deal in May.
The central bank said in a statement on state television: “The recent developments in the foreign exchange and gold markets are largely due to a conspiracy by enemies with the aim of exacerbating economic problems and causing public anxiety.”
In May, President Donald Trump withdrew the US from the Iran nuclear deal, struck in 2015 between world powers and Tehran, under which international sanctions were lifted in return for curbs on its nuclear programme.
The USA will now begin reimposing economic sanctions on August 7, and has told countries they must stop imports of Iranian oil from November 4 or face their own financial measures.
Sanctions reimposed by Washington will be those on Iran’s purchase of US dollars, its trade in gold and precious metals and its dealings with metals, coal and industrial-related software.
Experts have warned that the reintroduction of the financial sanctions could see Iran’s oil exports plummet by up to two-thirds this year.
Mr Trump has called the Iran nuclear agreement one of the worst deals ever negotiated but Iran’s European partners in the agreement are preparing a package of economic measures of their own in a bid to salvage the accord.
But France has said it is unlikely that European nations will be able to put the package together before the November 4 deadline on stopping imports of Iranian oil.
Tensions between the US and Iran have been at an all-time high in recent days after a senior Iranian military commander hinted on Thursday that Iran is prepared to launch a war and wage a campaign of terror against the United States.
Major-General Qassem Soleimani was responding to an explosive tweet from Mr Trump last Sunday night directed at Iran.
The US President had written on Twitter: “To Iranian President Rouhani: NEVER, EVER THREATEN THE UNITED STATES AGAIN OR YOU WILL SUFFER CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE.
“WE ARE NO LONGER A COUNTRY THAT WILL STAND FOR YOUR DEMENTED WORDS OF VIOLENCE & DEATH. BE CAUTIOUS!”
The Iranian military commander has claimed that if the US starts a war, “Iran will finish it”.
Mr Soleimani, who heads up the Quds Force of Iran’s powerful Revolutionary Guards Corps, was reported by various Iranian news agencies as having made his comments during a speech in the city of Hamedan.
He said: “As a soldier, it is my duty to respond to Trump’s threats. If he wants to use the language of threat, he should talk to me, not to president Hassan Rouhani.”