Disclosures by Abd al-Qadir Khan, the father of Pakistan's nuclear programme, have in recent weeks opened the lid on a global black market network for sensitive nuclear technology that could be used to make atomic bombs.
Khan has admitted to leaking nuclear technology to Iran, Libya and North Korea.
"We have bought some things from some dealers but we don't know what the source was or from what country they came from," ministry spokesman Hamid Reza Asefi told a weekly news conference.
"It happens that some of those (dealers) were from some sub-continent countries," Asefi added, stressing that Tehran had informed the UN's nuclear watchdog - the International Atomic Energy Agency - about the purchases.
Malaysian police said on Friday Khan had sold centrifuge parts worth $3 million to Iran in the mid-1990s.
But Asefi said Iran, which insists its nuclear programme is geared solely to electricity generation, had "never pursued nuclear weapons and will not do so".