The companies served as a procurement network for Iran's Centrifuge Technology Company (TESA), which produces enrichment centrifuges for the Atomic Energy Organization of Iran (AEOI), the Treasury said.

The network was led by Iranian firm Bakhtar Raad Sepahan and its overseas affiliates. It also included a Chinese firm, Henan Jiayuan Aluminum Industry Company, which was also sanctioned.

Other sanctioned entities are front companies based in China and Belgium, the Treasury said.

"Treasury is taking action to shut down an Iranian nuclear procurement network that leverages Chinese- and Belgium-based front companies to acquire critical nuclear materials and benefit the regime's malign ambitions," said Treasury Secretary Steven Mnuchin in a statement.

"Iran cannot claim benign intent on the world stage while it purchases and stockpiles products for centrifuges."

The sanctions were announced ten days after AEOI said its resumed enrichment operations had surpassed limits placed by the 2015  nuclear deal, a deliberate move to press other parties into keeping their side of the bargain.

US President Donald Trump withdrew from the deal between Iran and six world powers in May 2018 and has since reimposed sanctions on many sectors including the crucial oil and financial industries.

Iran demanded the other parties -- France, Germany, Britain, China and Russia -- take steps to guarantee the economic benefits Iran was promised for the drastic limitations imposed on its nuclear program.

Trump warned last week that sanctions against Iran would be "increased substantially" after Tehran surpassed the enrichment cap in the 2015 deal.