Iran began fuelling its first nuclear power plant today after decades of delay and amid international fears it is seeking an atomic bomb and not just electricity.
Iranian television showed live pictures of Iran's nuclear chief Ali Akbar Salehi and his Russian counterpart watching a fuel rod assembly being prepared for insertion into the reactor.
"Despite all the pressures, sanctions and hardships imposed by Western nations, we are now witnessing the start-up of the largest symbol of Iran's peaceful nuclear activities," Mr Salehi told a news conference.
Russia has built and supplied the fuel for the Bushehr plant, work on which was initially started by German company Siemens in the 1970s, before Iran's Islamic Revolution.
The United States criticized Moscow earlier this year for pushing ahead with the start-up plans amid persistent Iranian defiance over its nuclear activities.
Moscow supported a fourth UN Security Council resolution in June, which imposed new sanctions and called for Iran to stop its uranium enrichment which, some countries fear could lead it to obtain nuclear weapons.
But Russia says a deal with Iran, under which it will both supply Bushehr and take back the spent fuel - which could be used to make weapons-grade plutonium - means it cannot help any Iranian efforts to build a bomb.
"The construction of the nuclear plant at Bushehr is a clear example showing that any country, if it abides by existing international legislation and provides effective, open interaction with the IAEA (International Atomic Energy Agency), should have the opportunity to access the peaceful use of the atom," Russian state nuclear corporation chief Sergei Kiriyenko told the news conference.
Iranian officials say it will take two to three months before the plant starts producing electricity once the uranium-packed fuel rods are moved into the reactor.
Iran remains under intense international pressure to stop uranium enrichment, something the West says it no longer needs to do as it can acquire nuclear fuel from abroad.
Tehran's refusal to cease enrichment has resulted in a series of UN sanctions and tougher unilateral measures by the United States, the European Union and elsewhere.
Iran insists it is not seeking a bomb and says it has a sovereign right to nuclear technology and uranium enrichment.
Reuters