(CNN)Three Australian nationals, including two who also hold British citizenship, have been detained in Iran.
In a statement sent to CNN Wednesday, Australia's Department of Foreign Affairs and Trade (DFAT) said it was providing consular assistance to the families of three Australians detained in Iran. DFAT would not comment further on the three cases due to privacy reasons, and would not confirm whether the cases were related.
According to a report by Australian state broadcaster ABC, one of the three is a British-Australian woman who has been behind bars for almost a year. The other two are a couple -- a British-Australian woman and her Australian boyfriend -- who were arrested in the past few months.
Britain's Foreign Office wouldn't confirm the ABC report, but said in a statement that UK Foreign Secretary Dominic Raab had met Iran's ambassador on Wednesday and "raised serious concerns about the number of dual national citizens detained by Iran and their conditions of detention."
The arrests come amid tensions between Iran and United States and its allies, including Australia and the UK. Since the decision by US President Donald Trump in 2018 to abandon the Iran nuclear deal, Washington has attempted to use what it calls "maximum pressure" to change Iran's behavior and limit its nuclear ambitions.
Earlier this year, tensions between the US and Iran soared to levels that prompted fears of a war. Oil prices jumped as investors feared that attacks on oil tankers risked a disruption of shipments in the Strait of Hormuz, which passes by Iran and is the most important place on the planet to the global supply of oil.
Last month, Australia's Prime Minister Scott Morrison announced the country's defense force would work alongside the US and the United Kingdom on a maritime security mission in the Strait of Hormuz.
Alistair Burt, the UK's former Middle East minister, described the detentions as a "hostage-taking" and "deeply worrying" during an interview with BBC's Radio 4 on Wednesday.
"The policy of effectively taking hostages, and that's how it looks, makes it very difficult for those who want a different relationship with Iran to get on the front foot with those who regard it as unremittingly hostile," Burt added.
UK business minister Andrea Leadsom added that reports of the detentions sound "extremely concerning" during an interview with Sky News on Wednesday.
"Iran once again ups the stakes," opposition Labour Party lawmaker Tulip Siddiq said in a post on Twitter. "This is a wake up call for our Prime Minister, Government and Ministers that they must act urgently to bring our innocent citizens home."
Nazanin Zaghari-Ratcliffe, a dual British-Iranian citizen from Siddiq's constituency in London, has been detained in Iran since 2016 on spying charges.
On Wednesday, a DFAT spokesperson urged Australian citizens and holders of dual nationality with Australia who are traveling to or through Iran to follow the government's latest travel advice.
Australia's latest travel advice for Iran is to "reconsider your need to travel," due to "the risk that foreigners, including Australians, could be arbitrarily detained or arrested," according to the Smartraveller website which was updated on Monday.
Citing recent military tensions, the government also warns travelers to stay away from military or nuclear sites which are not always clearly marked. Border areas with Afghanistan and Iraq are under the highest "do not travel" advisory.