Iran has finished moving a first cascade of advanced centrifuges from an above-ground plant at its main uranium enrichment site to an underground one in a fresh breach of its nuclear deal with big powers, a U.N. atomic watchdog report showed on Wednesday. The transfer to the underground plant apparently built to withstand aerial bombardment was done in response to the burning down of an above-ground centrifuge-building workshop at Natanz in July, which Tehran has called an act of sabotage. It also slowed Iran's output of enriched uranium, the report showed.