Australia is pushing Iran to give "fair and transparent treatment" to three Australian citizens being held under arrest in the Middle Eastern country.
Iran has acknowledged for the first time it is holding three Australians, including two with joint British nationality.
Iran's judiciary spokesman said the three had been charged in two separate cases.
Perth couple Mark Firkin and Jolie King were detained by Iranian authorities about 10 weeks ago.
The travel bloggers are accused of flying a drone near a restricted military zone in Tehran.
The third, University of Melbourne lecturer Kylie Moore-Gilbert, faces charges of spying for another country.
If convicted, Dr Moore-Gilbert could be jailed for 10 years.
Australian Trade Minister Simon Birmingham said Foreign Minister Marise Payne was dealing with the "very serious matters".
"We have expectations in relation to fair and transparent treatment of citizens, we will continue to advocate very clearly for that," Senator Birmingham told reporters in Canberra on Wednesday.
UK International Trade Secretary Liz Truss, in Canberra to negotiate a potential free trade deal, also addressed the arrests.
"Our foreign secretary Dominic Raab is very concerned about this issue and he's dealing with it," she told reporters.
The Australian government has been providing consular assistance to the three Australians, while Senator Payne has raised the issue with her Iranian counterpart several times.
Former foreign minister Julie Bishop has said she is prepared to use her longstanding relationships with Iranian leaders to lobby for the trio's release.
Australian Associated Press