"Men are ordered to grow their beards and trim their moustaches and anyone found violating this law will face the consequences," senior Hezb al-Islam official Moalim Hashi Mohamed Farah told reporters.
"To grow one's beard is a moral teaching left by our Prophet Mohamed, peace be upon him, so it is a duty to keep this religious practice alive and punish men who shave their beards and grow their moustaches," he said.
Mogadishu's male population appeared resigned to the new law, arguing that avoiding the wrath of the country's hardliners was worth the time and effort of a little extra facial grooming.
"The new law will affect almost every household in Mogadishu because most men don't grow beards here," said Hasan Muse, a clean-shaven Mogadishu resident.
"Personally, I don't have a problem growing a beard, it's just that you actually need more time to look after a proper beard than to simply shave," he argued.
Sabriye Mohamed, for his part, said he would continue to choose his own facial hair style because he lived in one of the few neighbourhoods still controlled by the Western-backed transitional federal government.
"I have heard the news about the law ordering men in Mogadishu to grow beards but it will have no impact on me because I live in the government-controlled area," he said.
Such rules are already being implemented in some parts of the city and other regions of Somalia by the Shebab group, which has a dedicated religious police branch known as "Jaysh al-Hisbah" (Army of morality).
Units from the movement's "social mobilisation brigades" can often be seen criss-crossing busy areas on pick-up trucks and blaring instructions through loudspeakers to join the jihad and respect a pure Islamic clothing style.
Some of the other edicts imposed on Mogadishu by Islamist insurgent groups include a ban on watching World Cup games in public, as well as bans on Western music, DVDs and video games.
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