Couples in Iran are defying the country's strict Islamic law by living together outside of wedlock, angering hardline clerics who call the practice is an insult to Islam.
The growing trend, known as 'white marriage' because of its association with the western world, has become so serious that Iran's Supreme Leader Ayatollah Khamenei has commented on it. His office issued a warning to the public and called on police and the judiciary to "show no mercy" to couples discovered cohabiting.
"It's shameful for a man and a woman to live together without being married," the statement said. "It won't take long for people who've chosen this lifestyle to have wiped out a legitimate generation with an illegitimate one."
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In a country where shaking hands with a member of the opposite sex is illegal, couples are risking their freedom and sometimes even their lives to live together.
Many couples are forced to lie to their families in order to protect them from the shame, and must always be on the alert for inquisitive neighbours and landlords who could tell the authorities.
"We are always very careful. When we leave the building, we take care that no one takes notice," one couple told Deutche Welle.
Although still largely unheard of in most rural areas, the practice is growing among young people in larger cities. The practice shows just how much attitudes among young Iranians have shifted in just one generation, writes BBC Persia's Rana Rahimpour.
Iran is facing a declining birth rate as couples are waiting longer to get married and have children. "Just like in the rest of the world, the middle class in Iran is starting to prefer this type of life to traditional marriage," sociologist Mahrdad Darvishpour told Deutche Welle.
"I decided to live with my boyfriend, because I wanted to get to know him better," says Sarah from Tehran."It's hard to get to know someone just by going to restaurants and cafes together."
Despite the threat from the Supreme Leader, the crackdown on the practice is unlikely to work, argues Said Peyvandi, an Iranian professor of social sciences. "The desire for freedom and independence among the younger generation is too great."
Darvishpour agrees. "What happens under the skin of a society cannot be controlled," he said.
"The government might try to use force to stop this, but young people will continue to move forward. Modernity cannot be stopped."
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