Iranian President Mahmoud Ahmadinejad has blamed enemies of his country for the sharp falls in its currency.
Since the start of the year, the rial has lost four-fifths of its value, and has fallen to fresh record lows against the US dollar, the BBC reports.
Reports from Tehran suggest the rial plunged 18% in Monday's trading and then another 9% on Tuesday.
Iranian Industry Minister Mehdi Ghazanfari has blamed speculators but US officials say the slide reflects the success of American economic sanctions targeted at Iran's controversial nuclear programme.
Mr Ahmadinejad said Western sanctions amounted to an economic war, but they would not stop the country's programme. "We are not people to retreat on the nuclear issue," he told a news conference
"Enemies have managed to reduce our oil sales but hopefully we will compensate for this," Mr Ahmadinejad said.
The central bank has placed a $US5,000 limit on the amount of foreign currency travellers can take in or out of Iran.
The US-led sanctions are being imposed on Iran because of the country's disputed nuclear programme.
The US accuses Iran of aiming to build nuclear weapons, while Iran counters that it simply wishes to develop nuclear power stations.
The sanctions, which are backed by the European Union, include a ban on the purchase of Iranian oil.