Two Australian citizens detained in Iran have been identified as Jolie King and Mark Firkin.
Ms King, who also holds a UK passport, and Mr Firkin were blogging their travels in Asia and the Middle East.
They were reportedly arrested 10 weeks ago near Tehran but news of the arrest, and that of another British-Australian woman, came to light on Wednesday.
Australia said it had repeatedly raised their cases with Tehran, including in a meeting between officials last week.
Foreign Minister Marise Payne said she had lobbied on their behalf in a meeting with her Iranian counterpart.
She described the detentions as “a matter of deep concern” on Thursday, and confirmed that assistance had been offered to the families of the three detainees.
“[We] hope to see Mark and Jolie safely home as soon as possible,” their families said on Thursday.
The situation comes amid growing tensions between the West and Iran.
Several dual nationals have been detained in Iran in recent years, including the British-Iranian woman Nazanin Zaghari-Ratcliffe.
Relations between the UK and Iran have also been strained in recent months by a row over the seizure of oil tankers in the Gulf.
Australia also announced in July that it would join the US and the UK in policing the Strait of Hormuz against Iranian threats.
Ms King – who has dual UK and Australian nationality – and Mr Firkin, an Australian citizen, were reported to have been travelling on Australian passports.
In 2017, the couple left Western Australia to embark on a major trip driving across Asia to the UK. They were documenting their adventures on Instagram and Youtube, where they had more than 20,000 followers.
Videos of their travel through a dozen countries featured their cultural interactions and often showed drone footage of the natural landscape.
“Our biggest motivation… is to hopefully inspire anyone wanting to travel, and also try to break the stigma around travelling to countries which get a bad wrap [sic] in the media,” the pair wrote online.