Some 500 Iranian demonstrators formed a human chain Tuesday at a key nuclear plant at the centre of a dispute between the Islamic republic and the international community.
"Nuclear energy is our right," chanted the demonstrators, most of them Islamist students, gathered outside the gates of the plant in Isfahan, 400 kilometres (250 miles) south of the capital.
"Let's stop the negotiations" with the European Union, they cried, carrying a banner which read "Isfahan is only the beginning".
Iranian technicians last week removed seals placed by the UN watchdog International Atomic Energy Agency (IAEA) at the uranium conversion plant, raising the stakes in a standoff with the international community.
The United States accuses Tehran of covertly developing nuclear weapons, a charge vehemently denied by Iran, which says its atomic programme is a peaceful effort to generate electricity.
Conversion turns uranium ore or yellowcake into a feed gas for making enriched uranium, which can be the fuel for reactors or the explosive core of atomic bombs.
Iran points out that its right to the nuclear fuel cycle is legally enshrined under the nuclear Non-Proliferation Treaty and that it has infringed no international rules by resuming uranium conversion.
Despite ending a nine-month freeze on sensitive nuclear activities that was agreed on during talks with Europeans, Iran's uranium enrichment as such remains suspended.