Iran has arrested some of those responsible for assassinations of its nuclear scientists, state media reported yesterday, in a continued hunt for those it says are working to sabotage its nuclear programme.

Intelligence Minister Heydar Moslehi said Iran had shut down two networks inside and outside the country he said were involved in training the killers.

At least four scientists associated with Iran's disputed nuclear works have been killed since 2010 and a fifth, Fereydoun Abbasi Davani, now head of Iran's Atomic Energy Organisation, was wounded.

The West believes Iran is stockpiling enriched uranium as potential fuel for nuclear weapons and trying to develop technology needed for a bomb. Iran denies this, saying its nuclear activity is solely for peaceful energy purposes.

Mr Moslehi did not say how many people had been arrested, for which killings they were allegedly responsible, or where the networks were operating.

"They took steps not to leave any clues behind but they were stricken by mistakes," he said.

Mr Moslehi spoke at a ceremony marking the first anniversary of the shooting death of Dariush Rezainejad. Initial reports in Iranian media suggested Mr Rezainejad was involved in Iran's nuclear programme, but later said he was an engineering student.

"We were able to arrest the main actors in this act of terrorism," Mr Moslehi was quoted as saying.

Iran blames the assassinations on US, Israeli, French, British and German spy agencies, especially the Israeli Mossad.

In May, Iran hanged 24-year-old Jamal Fashi for the murder of scientist Massoud Ali Mohammadi in January 2010, saying Mr Fashi had gone to Israel for training.