Iran has detained three Australian and British citizens in Tehran’s notorious Evin prison amid heightened tension in the Arabian Gulf. Australia's foreign ministry confirmed that three of its citizens were being held in Iran. <em>The Times, </em>which first reported the news, said two of the people are also British. If true, it is believed to be the first time for some years a British national without dual Iranian citizenship has been imprisoned by Iran. UK prime minister Boris Johnson and foreign secretary Dominic Raab are expected to raise the detention of British citizens with Iran at the UN general assembly later this month. On Tuesday, Mr Raab had already criticised Iran for its support of Houthi rebels in Yemen and the Hezbollah militant group. The British Foreign Office warns against all travel to Iran for dual British-Iranians, saying they “could be arbitrarily detained in Iran”. But for British citizens without Iranian nationality, the Foreign Office only cautions against all travel to areas bordering Afghanistan, Iraq, Pakistan and Turkmenistan. According to reports, a British-Australian lecturer has been sentenced to ten years in jail on unknown charges and is being held in solitary confinement, reports said. In a separate case, a British-Australian blogger was stopped 10 weeks ago with her Australian boyfriend. <em>The Times</em> quoted an unnamed source saying she was being detained as part of a prisoner swap effort. “The Department of Foreign Affairs and Trade is providing consular assistance to the families of three Australians detained in Iran. Due to our privacy obligations, we will not comment further,” said an Australian government spokesman. All three are being held at Tehran’s Evin Prison, where British-Iranian charity worker Nazanin Zaghari-Ratcliffe has been since 2016 on espionage charges. The UK's previous foreign minister Jeremy Hunt called on world powers to pull together to rally against Iran's actions. “Iran once again ups the stakes. This is a wake up call for our Prime Minister, Government and Ministers that they must act urgently to bring our innocent citizens home,” said Tulip Siddiq, the MP for Ms Zaghari-Ratcliffe’s London constituency. Her husband, Richard Ratcliffe, called on the British government to do more to protect ordinary citizens. Alistair Burt, until recently a UK foreign office minister for the Middle East, said: "Iran works on the basis of putting pressure on countries it believes are hostile to it. Hostage-taking has become part of the process and it’s deeply worrying.” Tension is particularly inflamed between London and Tehran after Iran's seizure in July of a British flagged oil tanker. It came only weeks after British troops stopped an Iranian vessel off Gibraltar that it said was headed to Syria in breach of sanctions. In April, Iranian Foreign Minister Mohammad Javad Zarif said that he had contacted the US government last November saying he was open to a prisoner swap between British-Iranian dual national Nazanin Zaghari-Ratcliffe and an Iranian woman in prison in Australia. “I feel sorry for them and I have done my best to help,” Mr Zarif said of Ms Zaghari-Ratcliffe and her family. She has been held for more than three years in a Tehran jail for what the UK government maintains are false charges. “But nobody talks about this lady in Australia who gave birth to a child in prison," Mr Zarif said. "I put this offering on the table publicly now: exchange them.” Robert O'Brien, US President Donald Trump's special envoy for hostage affairs, told <em>T<em>he National</em></em> earlier this year month that there would be "no concessions, no prisoner swaps, no pallets of cash" to secure the release of US citizens. However, he gave no indication of the US position regarding foreign nationals.