Mark Firkin and Jolie King are in Tehran's notorious Evin jail, along with an Australian-British university lecturer who has spent months detained there on a separate matter.

Mr Firkin and Ms King have travelled the world for more than two years, documenting their adventures on YouTube and Instagram.

But followers sounded the alarm about 10 weeks ago after their regular updates dried up.

Their intrepid travels had taken a dark turn, with the young couple thrown behind bars.

The Perth couple's families have now spoken publicly for the first time.

"Our families hope to see Mark and Jolie safely home as soon as possible," they told AAP on Thursday.

"We have no further comment to make at this stage and ask that the media respects our privacy at this difficult time."

Drone use with a permit is allowed in Iran, but there are strict conditions.

People must not fly drones over people or large crowds, over the city of Tehran, or over sensitive areas.

Flying a drone without a permit in Iran is punishable by six months in prison followed by immediate deportation.

The lecturer has been imprisoned for several months and has reportedly been given a 10-year prison sentence.

While the allegations against her remain unclear, such penalties are routinely given in Iran for spying charges.

The notorious Evin prison is where Iran holds its political prisoners and has a reputation for being the scene of various human rights abuses, including summary executions.

Foreign Minister Marise Payne said the detainment of the three Australians was a matter of deep concern.

Senator Payne has met with her Iranian counterpart several times to press for their release, as recently as last week.

"The government has been making efforts to ensure they are treated fairly, humanely and in accordance with international norms," she told parliament.

"We also continue to provide consular assistance to the three Australians' families, with whom we have maintained regular contact.

"On the basis of ongoing discussions, I continue to believe that the best chance of a successful outcome for these three Australians is with Iran through diplomatic channels and not through the media."

Prime Minister Scott Morrison was also reluctant to provide much comment on the "very sensitive" cases.

"They're never issues that are addressed well by offering public commentary on them," he told reporters in Canberra.

The foreign minister said there was nothing to suggest the detainments were related to an Australian military deployment to the Strait of Hormuz, or international unrest about Iran's nuclear program.

Senator Payne urged Australians thinking about visiting Iran to follow her department's advice.

Australia's official travel advice for Iran is currently set to "reconsider your need to travel".

The highest warning level - "do not travel" - applies in some parts of the country.

There is a risk that foreigners, including Australians, could be arbitrarily detained or arrested.

The advice states Australians may be at greater risk if they have a profile that is viewed adversely by Iran, or undertake activities which could attract the attention of its authorities.

Australian Associated Press