President Ahmadinejad has accused Israel and western governments for previous killings of scientists [GALLO/GETTY]

An Iranian nuclear scientist has been shot dead in the country's capital Tehran, according to reports in Iranian media.

Dariush Rezai-Nejad was killed in front of his house in the east of the city when two gunmen on motorcycles opened fire.

Al Jazeera's Dorsa Jabbari, reporting from Tehran where she spoke to witnesses, said Rezai-Nejad's wife was also wounded and had been taken to a nearby hospital.

"He 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," our correspondent said.

"According to Fars news agency, he worked for the defence department and had links with the country's nuclear program as well. But we do not know exactly to what extent he was involved."

String of attacks

There has been no official response from the Iranian government yet.

"What is clear is that this is a huge blow to the country's intelligence units. Rezai-Nejad's residence, in the eastern part of the city, was within close proximity of the intelligence ministry headquarters," our correspondent said.

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 programmes.