Turkish and German security forces swooped simultaneously on smugglers in both countries who were apparently trying to move nuclear materials from Germany and India to Iran, Turkish media reported.
The Turkish Haberturk newspaper reported Sunday that an Iranian-born Turkish citizen in Istanbul was nabbed at Ataturk airport along with another Iranian suspect, reported to be a key figure in the operation.
Turkish authorities also raided a house owned by an Iranian couple, but the suspects were not found and are being sought.
In Germany, authorities apprehended another five Iranian suspects.
The ring is suspected of buying parts in India and Germany to be sent to Iran for use in its Arak nuclear facility.
Two weeks ago the Daily Telegraph reported that satellite images of the Arak nuclear site showed that a heavy water facility was in operation.
Heavy water can be used to produce plutonium, an alternative to uranium in making an atomic bomb. International inspectors have been barred from visiting the heavy water plant since 2011.
In February German authorities charged two Iranians with supplying Iran during 2008 and 2009 with over 60 engines to be used for its drone aircraft program.