Australian couple Jolie King and Mark Firkin are back in Australia after being released from an Iranian jail.

Key points: Jolie King and Mark Firkin had been detained in Tehran for several months after reportedly flying a drone without a permit

Jolie King and Mark Firkin had been detained in Tehran for several months after reportedly flying a drone without a permit The pair had been travelling around the world since 2017 and documenting their adventures online

The pair had been travelling around the world since 2017 and documenting their adventures online It was later revealed that an Iranian scientist in custody in Australia would not be extradited to the US, despite being ruled eligible by a magistrate

In a statement released through DFAT, the couple said they were "extremely happy and relieved to be safely back in Australia with those we love".

Hours after their release, Attorney-General Christian Porter revealed that an Iranian scientist who had been studying in Brisbane would not be extradited to the United States, despite a magistrate having ruled he was "eligible for surrender" to the nation.

The Perth couple had been detained for several months after being arrested for reportedly flying a drone without a permit. They had been travelling around the world since 2017 and documenting their adventures online.

All charges against them have now been dropped.

"While the past few months have been very difficult, we know it has also been tough for those back home who have been worried for us," they said.

"We are grateful for the efforts of the Australian Government in helping secure our release, and we thank our family and friends for their love and support.

"While we understand the intense public interest, we do not wish to comment further at this time and request the media let us and our families get back to our normal lives.

"We know there are others who remain in detention in Iran, including a fellow Australian, and believe intense media coverage may not be helpful for efforts to bring them home."

Foreign Minister Minister Payne said the Government went "through diplomatic channels … to secure their release". ( ABC News: Matt Roberts )

Foreign Affairs Minister Marise Payne said the travel bloggers were in "good health and in good spirits" and had been united with their families.

She said the couple's return was a "source of great relief and joy for everyone".

"The Government has worked very hard through diplomatic channels … to secure their release as well as to ensure they were treated appropriately while they were detained," she said.

"We have done that discreetly and I would note that each case of an Australian unfortunately detained overseas is different and requires a specific and particular response."

Iranian scientist will not be extradited to US

Later on Saturday Iranian state TV showed University of Queensland research student Reza Dehbashi Kivi returning home after 13 months in custody in Australia over allegations he exported American equipment for detecting stealth planes or missiles to Iran, circumventing US sanctions.

Footage shows Mr Dehbashi Kivi wiping tears from his eyes as he walked into Tehran's Imam Khomeni international airport.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 46 seconds 46 s Iranian scientist released from Australian custody, arrives in Tehran

Mr Porter would not say if the two cases were linked, saying "extradition requests are considered on a case-by-case basis".

"The Australian Government does not comment on the details behind its consideration of particular cases," he said in a statement.

"And while it is likely that because of Mr Dehbashi Kivi's nationality some will speculate regarding this matter, consistent with prior practice I do not intend to comment further on the particular details of this case, particularly when any such response from me may diminish our Government's capacity to deal with future matters of this type in Australia's best interests."

Former diplomat Bruce Haigh said his "inclination would be that it's part of a deal", but if the two cases were connected Australia likely would have consulted with the United States before an exchange.

"There's nothing in recent time that would indicate that we'd want to push back against the United States in any way," he said.

PM welcomes King and Firkin home

Senator Payne had raised the release of Ms King and Mr Firkin with the Iranian Government at a recent summit, and had been in face-to-face talks with Iran's Foreign Minister Javad Zarif.

All charges against the couple have been dropped. ( Instagram: Jolie King )

Prime Minister Scott Morrison took to Twitter to welcome the news of the pair's release.

"Great to have Jolie and Mark home. Thanks to the whole team involved in bringing them home."

Ms King is a dual Australian-British citizen and the UK Government had demanded the couple's release, with British Foreign Secretary Dominic Raab contacting the Iranian ambassador.

The UK Foreign Office said Mr Raab "raised serious concerns about the number of dual national citizens detained by Iran and their conditions of detention".

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 7 seconds 1 m 7 s Jolie King and Mark Firkin posted about their travels through Pakistan in June, before they were detained in Iran.

Online followers had raised concerns after the bloggers did not post for several weeks.

"Hey you guys, we are getting worried, no post or episode for over a month," one wrote. "Hope you are both well and safe."

They were being held at the notorious Evin jail, north of Tehran, which is used to house political prisoners.

'We don't accept the charges'

Another Australian, Melbourne academic Kylie Moore-Gilbert, remains incarcerated in the same prison.

The ABC understands Dr Moore-Gilbert has been convicted of espionage and sentenced to 10 years in jail by Iranian authorities.

Dr Moore-Gilbert is a Middle East expert at the University of Melbourne's Melbourne Asia Institute. ( University of Melbourne )

In a statement issued via the Department of Foreign Affairs and Trade (DFAT) in September, her family thanked the Government and the University of Melbourne for their "ongoing support at this distressing and sensitive time".

Dr Moore-Gilbert is a Middle East expert at the University of Melbourne's Asia Institute, specialising in Arab Gulf states. She has also studied at Cambridge.

She was arrested and convicted late last year.

"The Australian Government is continuing to seek her return to Australia and discussions with authorities in Iran are ongoing," Senator Payne said.

"They are very long-term negotiations and they are ongoing.

"She has been detained some considerable time and has faced the Iranian legal system and been convicted and sentenced. We are continuing our discussions with the Iran government, we don't accept the charges upon which she's been convicted and we would seek to have her returned to Australia.

"The situation is very complex."

The University of Melbourne said last month it had been in close contact with the Australian Government and Dr Moore-Gilbert's family and would not be providing further comment about the "sensitive matter".