Concerns continue to grow that Iran's nuclear ambitions go beyond power generation.
Country 'still has nuclear military' aims
Global action against Iran has been steadily building over the country's nuclear intentions.
The US, UK and Canada last week increased restrictions on Iran's finance and energy sectors in an attempt to put pressure on Tehran to abandon its suspected nuclear-weapons programme.
A report released this month by the International Atomic Energy Agency (IAEA), the UN nuclear watchdog, suggested Iran could still be working towards nuclear military ambitions, which Tehran denies.
The US says the entire Iranian financial sector, including its central bank, is involved in money laundering. Any institution or company that engaged in transactions with the country's banking system is at risk of supporting Iran's illicit activities, US officials warn.
Companies that provide goods or services to Iran's oil and gas industries are also targeted by new US sanctions. Most international oil companies have already left Iran in the face of increasing global sanctions and the new measures aim to stop the country getting hold of technology and investment from smaller foreign firms.
Also last week, the UK announced it was imposing sanctions against Iran that would cut off all UK financial ties with Iranian banks, including the central bank.
Canada said it was barring almost all transactions with Iran. The EU said it planned to impose further sanctions on Thursday.
The IAEA report said Iran had carried out tests "relevant to the development of a nuclear device".
* Tom Arnold