The Iranian parliament's backing on Tuesday of a plan to end nuclear inspections after the assassination of the country's top nuclear scientist has met immediate opposition from the government.

Deputies supported a draft bill "for the lifting of sanctions and protection of the Iranian people's interests", saying they want to achieve the objectives of "martyred" scientist Mohsen Fakhrizadeh.

Fakhrizadeh was assassinated on a major road outside Tehran on Friday in a bomb and gun attack that the Islamic republic has blamed on its arch foe Israel.

"The government has explicitly announced that it does not agree with (this) plan" which it considers "neither necessary nor useful", foreign ministry spokesman Saeed Khatibzadeh told a news conference Tuesday.

The draft bill calls on the government to end inspections of Iran's nuclear facilities by the UN and to "produce and store 120 kilogrammes per year of uranium enriched to 20 percent".

Such steps would run counter to commitments made by Iran as part of a landmark nuclear deal agreed with world powers in 2015.

The 2015 deal offers Iran relief from sanctions in exchange for curbs on its nuclear programme and UN-verified safeguards to prove it is not developing nuclear weapons. 

The Islamic republic has always denied it is seeking such weaponry.

But the multilateral accord has been hanging by a thread since 2018, when President Donald Trump unilaterally withdrew the United States and reimposed sanctions that have battered Iran's economy.

The Islamic republic has retaliated by gradually rolling back most of its commitments under the nuclear deal.

In its latest report last month, the International Atomic Energy Agency (IAEA) said Iran had enriched uranium over the 3.67 percent limit set out in the 2015 accord.

The UN's nuclear watchdog said that Iran had not exceeded the threshold of 4.5 percent and that the country was still complying with its strict inspections regime.

In an interview with AFP on Monday, IAEA chief Rafael Grossi said Iran has nothing to gain from ending inspections of its nuclear facilities.

"We understand the distress but at the same time it is clear that no-one, starting with Iran, would have anything to win from a decrease, limitation or interruption of the work we do together with them," Grossi said.