The European Union voiced "serious concern" Friday over Iran's decision to install more modern equipment at its Natanz nuclear plant, saying it would be in "clear violation" of its international obligations.

"We have learned with serious concern that Iran has informed the IAEA about its intention to install advanced centrifuges of the type IR2m at the Fuel Enrichment Plant at Natanz," said a spokeswoman for EU foreign policy chief Catherine Ashton.

Their installation could significantly increase the production of enriched material, she said.

This would "add to the already severe concerns of the international community about the exclusively peaceful nature of Iran's nuclear programme" and would be "in clear violation of Iran's international obligations to suspend all enrichment and enrichment related activities."

"We urge Iran to fully comply with its international obligations," the EU spokeswoman said.

An IAEA document seen Thursday by AFP showed that Iran intends to install more modern equipment at Natanz, one of its main nuclear sites.

The UN atomic agency document said that Iran informed it in a letter dated January 23 that "centrifuge machines type IR2m will be used in Unit A-22" at the Fuel Enrichment Plant (FEP) at Natanz.

A Vienna diplomat told AFP on condition of anonymity that the new machines would likely be used to enrich uranium to fissile purities of five percent.

Of greater concern than Natanz is Iran's Fordo site, which enriches uranium to 20-percent purities, significantly closer to the 90-percent level needed for a bomb.