Iran said on Wednesday it plans a nearly 10-fold expansion of its uranium enrichment capacity in the next five years, denying a U.N. report which said its nuclear activities had slowed.

"Our plans to install and run centrifuges is not based on political conditions ... We have neither slowed down or accelerated our work there," Gholamreza Aghazadeh, head of the Atomic Energy Organization of Iran, told a news conference.

He was speaking in southwestern coastal town of Bushehr where Iran is building its first nuclear power plant. Iran said on Wednesday it had carried out successful tests at the Russian-built plant, taking it a step closer to its launch.

The visiting head of Russia''s state nuclear company, Sergei Kiriyenko, hailed "significant improvements" in the Islamic Republic''s first such plant to produce electricity.

Aghazadeh said Iran would over the next five years install 50,000 centrifuges used to enrich uranium at its Natanz plant in the central desert, up from the 6,000 he said were now running.

"We will increase our activities to install more by the end of next (Iranian) year (to March 2010)," he said.

He did not specify whether all 6,000 were enriching uranium. Iran was feeding uranium into just under 4,000 as of February 1 but had another 1,600 installed with most being tested at the time, the International Atomic Energy Agency said last week.