Iran said on Saturday it is removing the fuel from the reactor of a Russian-built nuclear power plant, a move seen as a big blow to its controversial nuclear programme.

The decision to remove the fuel from the reactor of the nuclear plant in the southern city of Bushehr comes just months before the facility -- which has seen a roller-coaster ride since its construction began in the 1970s -- was scheduled to generate electricity.

"Based on the recommendation of Russia, which is in charge of completing the Bushehr atomic power plant, the fuel inside the reactor core will be taken out for a while to conduct some experiments and technical work," Iran's envoy to the UN atomic watchdog, Ali Asghar Soltanieh, told the ISNA news agency.

"After the experiments, it will again be installed in the core of the reactor." He did not specify when the experiments would be completed.

Iran had started loading the fuel into the reactor in October after the "physical launch" of the plant by Moscow on August 21.

In January, Iran's former atomic chief Ali Akbar Salehi said the plant would be ready to generate electricity on April 9 after operations began in November.

The decision to remove the fuel rods, also supplied by Russia, is the latest setback in the more than three-decade old history of the plant, which was first launched by the US-backed shah using contractors from German company Siemens.

But it was shelved when the shah was ousted in the Islamic revolution of 1979 and it lay unfinished through the 1980s as Iran battled internal opposition and a devastating eight-year war with Iraq.

It was revived in the late 1980s after current supreme leader Ayatollah Ali Khamenei succeeded revolutionary leader Ayatollah Ruhollah Khomeini.

In the early 1990s, Iran sought help for the project after being turned away by Siemens over nuclear proliferation concerns.

In 1994, Russia agreed to complete the plant and provide the fuel, with the supply deal committing Iran to returning the spent fuel.

A deal was finally signed in January 1995 after 18 months of negotiations and preliminary accords.

That was just the start of a spate of delays and setbacks, as the Russian contractor was repeatedly forced to postpone completion.

In 2007, Russian contractor Atomstroiexport even accused Iran of falling behind in its payments, further jeopardising the project's completion.

But finally on August 21 last year, Russian and Iranian engineers declared the physical launch of the plant, a move undertaken despite Moscow hardening its stance against Tehran's nuclear programme by voting for a new sanctions resolution at the UN Security Council.

The West, which suspects Iran's nuclear programme is cover for a weapons drive -- a charge vehemently denied by Tehran -- does not see Bushehr as posing any "proliferation risk," however.

The plant has faced hiccups even after its physical launch, with officials blaming the delays in generating electricity on a range of factors, including Bushehr's "severe weather."

But they deny it was hit by the malicious Stuxent computer worm which struck industrial computers in Iran, although they acknowledge that the personal computers of some personnel at Bushehr were infected with it.

In January, The New York Times reported that US and Israeli intelligence services collaborated to develop the Stuxnet virus to sabotage Iran's nuclear programme and the Bushehr plant could have been one of the targets.

On Saturday, Nasser Rastkhah, head of Iran's nuclear safety system, reiterated to state news agency IRNA that Stuxnet had "no effect on the controls of the Bushehr atomic plant."

Bushehr is a pressurised water reactor with a capacity to produce 1,000 megawatts of power.

It was constructed by more than 2,000 Russian engineers and workers living in a purpose-built village near the site.

Iran, which has some of the world's largest oil and gas reserves, says it wants to develop nuclear power so it can use those reserves judiciously.