The BBC reports:

The Iranian authorities have arrested a “network of spies” which they say was behind the assassination of a nuclear scientist a year ago, state TV reports.

In a brief statement, the authorities said the network was linked to Israel’s Mossad secret service.

Iran blamed US and Israeli agents for the killing at the time.

Separately, US Secretary of State Hillary Clinton has said international sanctions have slowed Iran’s progress towards developing nuclear weapons.

Massoud Ali Mohammadi, a 50-year-old university lecturer at Tehran University, was killed by a remote-controlled bomb on 12 January 2010 as he left his home in Tehran.

Iran’s intelligence ministry said Mossad had used bases in certain European and non-European countries as well as Iran’s neighbouring states for the purpose of the assassination, as well as other activities, Fars news agency reported.

The ministry said months of complicated measures and access to sources in the Israeli regime led to the finding of “very important and sensitive” information about Mossad spy teams, which inflicted heavy damage on Israel’s information and security structures, Fars reported.

Iran has blamed the intelligence services of Israel, the US and the UK over bomb attacks against two top nuclear scientists in November last year, Majid Shahriari, who died, and Fereydoon Abbasi Davani, another top nuclear expert who was wounded in a similar attack.

At the time, Iran’s state media said Mr Mohammadi had been assassinated by counter-revolutionaries, Zionists and agents of the “global arrogance”.

Washington later dismissed the accusation as “absurd”.