Shacking up is becoming a new trend in one of the most surprising of places: Iran.

A growing number of young couples are very quietly living together without marriage, which is illegal and, the government charges, is undermining Islamic values, reports the Los Angeles Times. Leaders have called it shameful and disgusting, and last year shut down a women's magazine that presented a feature on cohabitation, which is known in Iran as "white marriage."

"The Islamic ruler should strongly fight [against] this kind of life," said supreme leader Ayatollah Ali Khamenei's chief of staff. Officials should "show no mercy" in cracking down on the practice, he added.

Many of the couples wear fake wedding bands in an effort to avoid trouble.There's officially a hard line against white marriage and participants could be arrested, fined and even flogged. But large segments of the population are more progressive than government and religious rulers, particularly young people, and 30% of the population is younger than 30.

Cohabiting before marriage is economical

Everything forbidden — dancing, drinking, sex out of wedlock — is being enjoyed underground, women's rights expert Nina Ansary tells The Times.

"Many Iranians cohabit before marriage," she says. "It's economical. It's a way to date and live together and not be bound by the heavy weight of marriage in a country that handicaps its youth at every turn."

Women in particular are becoming more reluctant to wed, in part because they can be trapped in an unhappy marriage; divorce is much more difficult for a woman to obtain.

There's one other unusual option for the traditional marriage-averse: sigheh, which is a temporary marriage under Islamic law. The short-term contract allows sex, and can last hours or be extended for decades — and doesn't require divorce.