|Ahmadinejad has accused Israel and western governments for previous killings of scientists [GALLO/GETTY]
Iranian state television has denied that a man killed in his Tehran home on Saturday was a nuclear scientist.
Dariush Rezainejad was shot dead by two men on motorbikes as he entered his garage with his wife and child.
Iranian newspapers first reported that Rezainejad, 35, was working in the country's nuclear programme, which would have made him the fourth nuclear scientist to die or go missing in suspicious circumstances.
On Sunday, state television said he was a masters student in electronics at Khajeh University in Tehran and had worked for the defence ministry, though it was unclear in what capacity.
Ali Larijani, the speaker of parliament, denounced the killing in an address to legislators as the work of Zionists and the United States and said it showed Washington's hostility to Iran.
Larijani has previously served as a negotiator with the West on the country's nuclear programme.
Rezainejad's wife was also wounded and had been taken to a nearby hospital.
Al Jazeera's Dorsa Jabbari, reporting from the capital, said: "He [Rezainejad] was entering his garage with his wife at about 4:30 pm local time when two men on motorbikes approached and called him out by his name.
"When he turned around to respond, he was shot in the neck. His wife then ran to get help for her husband, she was chased and also shot.
"What is clear is that this is a huge blow to the country's intelligence units.
"Rezainejad's residence, in the eastern part of the city, was within close proximity of the intelligence ministry headquarters."
Over the past years, several Iranian nuclear scientists have been killed or injured.
In two separate attacks in 2010, Majid Shahriari and Massoud Ali Mohammadi were killed while Feriedoun Abbasi, the current head of Iran's Atomic Energy Organisation, was injured.
Mahmoud Ahmadinejad, the Iranian president, has accused Israel and western governments of being behind the killings of the prominent scientists.
After the death of Shahriari last year, Ahmadinejad said that "undoubtedly the hand of the Zionist regime and western governments is involved'' in the killing.
He said then that the killings would not stop Iran from pursuing its disputed nuclear programme.