Iran has begun efforts to shift its nuclear enrichment programme to an underground bunker where it could attain nuclear status safe from the threat of attack.
Installation of centrifuge and other manufacturing equipment was at a preparatory stage at Fordow, a facility deep inside a mountain near Qom, the country's holiest city, intelligence reports said.
"They are preparing [for the centrifuges to be installed] in Fordow," a diplomat briefed on the latest intelligence said.
Fereidoun Abbasi, the head of the Iranian nuclear programme, said this month that Iran would triple output of uranium enriched to 20pc, the threshold level from which a nuclear bomb -- made from material enriched to 90pc -- was relatively easy to produce.
The International Atomic Energy Agency (IAEA) expressed concern over continuing access to the facility.
The IAEA reported that by May 21 no centrifuges -- cylindrical machines that spin at supersonic speeds to enrich uranium -- had been introduced into the facility.
Leading experts believe that the shift to the mountain facility would increase the danger of Iran successfully launching a final push to make a bomb. "We see Iran moving in the direction of becoming a nuclear weapons-capable state," said Olli Heinonen, a former head of UN nuclear inspections worldwide.
But Iran's foreign minister, who is in Vienna for nuclear talks, said the country had disavowed nuclear weapons.
"Our Supreme Leader explained that the production and use of atomic weapons is wrong, not only in terms of foreign policy but on religious grounds," said Ali Akbar Salehi. (© Daily Telegraph, London)