The Islamic State (IS) group has reportedly issued a decree ordering all men in the Iraqi city of Mosul to grow beards on the grounds that the shaving of facial hair is haram (forbidden) under Shari'a law.

A report of the new IS decree in Mosul was posted on the Mosul Eye Facebook page on April 28. Mosul Eye is the pseudonym of a local historian who has been secretly documenting IS's activities in Mosul since the militants overran the city in June 2014. While it is not possible to verify the blogger's identity, Iraq watchers believe the accounts are credible.

Mosul Eye also posted a photograph of a leaflet that the account says IS has distributed in Mosul. The leaflets explain the Shari'a law basis for the IS edict to grow beards.

Those who fail to comply with the order to grow facial hair will be subject to punishment, Mosul Eye said.

IS militants have reportedly issued similar bans on shaving beards in other parts of Iraq and Syria, also based on the group's radical interpretation of Shari'a law.

British-based monitor the Syrian Observatory for Human Rights (SOHR) said in December that IS had imposed such a ban in the city of Al-Mayadin in eastern Syria. The group also banned Al-Mayadin residents from wearing engagement rings, on the grounds that this is a Christian tradition, SOHR said.

IS is not the first radical Islamist groups to impose mandatory beard-wearing on men living in lands under their control, however.

In 2010, militants from the Hizbul-Islam group in Somalia ordered men in Mogadishu to grow their beards and trim their mustaches.

"Anyone found violating this law will face the consequences," a Hizbul-Islam militant threatened.

The main role model for mandatory beard growth, however, is the Afghan Taliban, which during the height of its rule between 1996 and 2001 instigated a strict facial hair regime.

Shaving was, of course, banned (other things banned by the Taliban included kites, girls' schools, cassette tapes and women going out without a male relative).

Afghan men's beards had to be long enough to exceed a fist clasped at the chin. Some reports said that the Taliban had developed even more creative ways to check whether a man's beard met the religiously mandated length, with "morality" police asking men to put their beards inside a lantern glass to see if it fit. (Those whose beards were deemed too short were, of course, punished.)

In reaction to the radical Islamist predilection for beards, there are reports that some countries with a particular fear of IS have associated facial hair with radicalization.

In some cases, pogonophobia -- fear of beards -- has been taken too far.

Police in Tajikistan this week have been reprimanded for forcing Muslim men to shave off their beards.

Deputy Interior Minister Ikrom Umarzoda told RFE/RL on April 27 that two law enforcement officers in the northern Sughd region were officially rebuked after local residents complained that they were forced to shave their beards.

"We have ordered regional police departments to talk to local residents about extremism, but have never called on them to work with people through force and pressure," Umarzoda said.

In Afghanistan, the Taliban's beard obsession resulted in many Afghans fearing not only the bearded Taliban but also bearded Western special operations forces, Foreign Policy noted back in 2009.

"In Kandahar Province’s Zhari district, elders refer to the 'bearded Americans,' who they say behave very badly, and the 'shaven Americans,' who aren’t so bad," Foreign Policy reported.

Yet the association of beards with wild, untamed "Eastern" cultures dates back far earlier than the modern phenomenon of the radical Islamist.

In 1698, Russia's Peter the Great declared a war on facial hair as part of his modernization policies, imposing a mandatory beard tax on Russians, from noblemen to peasants, who refused to shave.

In contemporary Syria and Iraq, it is not only IS who are promoting the beard as a religiously mandated concept. Militants from other Islamist groups wear beards also, though none have gone as far as to impose an edict making facial hair mandatory.

While female militants cannot, of course, grow beards, a group of Chechen women supporters of the North Caucasian group Jaish al-Muhajireen wal-Ansar are supporting their men by developing a range of beard care products. The first of these, a beard shampoo, is named "Desire to Jannat," and is designed "for growth, thickness and 'taming'" one's beard. The ingredients include aloe-vera gel, jojoba oil, palm butter, cobra oil, and glycerin.

-- Joanna Paraszcuk