The group has been detained for alleged acts of spying, such as taking soil samples from restricted areas, according to state TV.

"These spies were taking earth samples in Iran's central desert where the Revolutionary Guards' aerospace missile exercises were conducted," they said.

Footage was shown of Giles Whitaker and his family in central Iran, where he appeared to be taking ground samples.

State TV said this was near where a missile test was taking place and that Mr Whitaker had been expelled from the area after apologising.

Also among those detained was the husband of Austria's cultural attaché in the country and a Polish university professor who had been visiting Iran as a tourist, the report said.