The couple were in Iran as part of a trip that started in Australia three years ago, the paper reported.
ABC reported the two cases were not connected.
There was no immediate comment Wednesday from Iranian officials, nor state media.
Cases involving dual nationals typically end up in closed-door hearings of Iran's Revolutionary Court, where former detainees say they had no opportunity to defend themselves against spying charges or offer evidence.
Analysts and family members of dual nationals and others detained in Iran long have said hard-liners in the Islamic Republic's security agencies use the prisoners as bargaining chips in negotiations with the West.
A UN panel in 2018 described "an emerging pattern involving the arbitrary deprivation of liberty of dual nationals" in Iran, which Tehran denied.
A prisoner exchange in January 2016 that freed Washington Post journalist Jason Rezaian and three other Iranian-Americans also saw the US make a $400 million cash delivery to Iran the same day, which involved money from a weapons sale in the era of the late Shah Mohammad Reza Pahlavi.
Several British nationals with Iranian backgrounds are similarly held as Iran and the UK have been discussing the possible release of some 400 million pounds held by London since the 1979 Islamic Revolution for a tank purchase that never happened.
Detentions of those with Western ties have spiked in the past around sensitive times in Iran.
Tensions between Iran and the US remain high over Tehran's unraveling 2015 nuclear deal with world powers, which President Donald Trump unilaterally withdrew America from over a year ago.
Australia has advised its citizens to "reconsider your need to travel" to Iran, the highest warning on a four-tier scale after "do not travel" to a country.
The UK and Australia last month signed onto a US-led maritime security mission to protect international shipping in the Strait of Hormuz, where Iran’s recent seizures of vessels has raised tensions with the West.
Agencies contributed to this report.
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