Enriched uranium can be used to produce nuclear fuel or atomic weapons.
IAEA spokeswoman Melissa Fleming confirmed that the process is being conducted under the agency's supervision.
The disclosure comes at a time of continuing controversy over Iran's nuclear program. The United States has accused Tehran of trying to develop nuclear weapons, but Iran says its program is purely for peaceful purposes.
Iranian President Hojatoleslam Mohammad Khatami said again today that his country will not give in to foreign pressure on its nuclear intentions.