Iran officially confirmed it has stepped up uranium enrichment by injecting gas into a second network of centrifuges, a state-run newspaper reported on Saturday.
The injection of gas into a second cascade of centrifuges marked Iran's first known uranium enrichment since February.
"We have exploited products from both cascades," the Iran Daily newspaper quoted Mohammad Ghannad, deputy head of Iran's Atomic Energy Organization, as saying on Saturday.
"The second one was installed in the past two week."
Ghannad said both cascades were enriching uranium by 3 to 5 per cent, enough for industrial use but not for weapons.
"This experience will help Iranian engineers get closer to industrial uranium enrichment," he said.
The UN's nuclear watchdog, the International Atomic Energy Agency, has been aware of the second cascade for the past five months, Ghannad said. "IAEA inspectors visited the cascades in Natanz last week," he said.
Injecting gas into centrifuges can either yield nuclear fuel or material for a warhead, but doesn't represent a major technological breakthrough and is unlikely to bring Iran within grasp of a weapon.
However, Tehran's announcement signaled the Islamic Republic's resolve to expand its atomic program at a time of divisions within the UN Security Council over a punishment for Iran's defiance.