An Iranian nuclear scientist has been shot dead in the capital, Tehran, Iranian media sources have said.
The scientist, who has not yet been named, was shot outside his home, the Isna news agency reported, adding that his wife was wounded in the attack.
In 2010, nuclear scientist Massoud Ali Mohammadi was killed by a remote-controlled bomb in Tehran.
Iran blamed that attack on Israeli secret service Mossad. Israel has long warned about Iran's nuclear programme.
Some reports said the latest attack involved assailants on a motorcycle, but this has not been confirmed.
In November last year, another Iranian scientist was killed in an attack in Tehran.
The US, Israel and many Western nations have opposed Iran's atomic programme, fearing it may be a front to creating a nuclear bomb.
Iran insists its nuclear programme is for purely peaceful purposes.
This week, Iran said it was installing newer and faster centrifuges at its nuclear plants, with the goal of speeding up its uranium enrichment process.
Enriched uranium can be used for civilian nuclear purposes, but also to build atomic bombs.
The French government condemned the move as a "new provocation".

http://www.bbc.co.uk/news/world-middle-east-14263126