It is the first time in the lawless Horn of Africa country that the insurgents, who seek impose a strict form of Islamic sharia law, have focused on men's appearance, having previously ordered women to cover their entire bodies, and banned bras.
We are ordering all men in Kismayu not to shave or trim their beards, but shave the moustache, Sheikh Ibrahim Garweyn, a senior Al Shabaab official for the public awareness in the southern Somali port town, told reporters on Saturday.
We will never accept to see men with long beards and moustaches together. They have three days to follow the order.
The group, which Washington says is an al Qaeda proxy, has already banned musical ringtones, dancing at weddings and playing or watching soccer.
Al Shabaab has carried out executions, floggings and amputations to enforce its rulings, mainly Kismayu.
The group is battling the government of President Sheikh Sharif Ahmed for control of Mogadishu, and is fighting a another Islamist militia -- Hizbul Islam --in the provinces.
Al Shabaab also ordered men to wear their trousers above the ankle. They have 15 days to follow the order, Garweyn said.
A two-and-a-half year insurgency has killed more than 19,000 civilians, displaced 1 million people, allowed piracy to flourish offshore and spread security fears in the region.Somalia has lacked a functioning central government since 1991. Its transitional government controls little more than a few blocks of Mogadishu, with the rest carved up between Al Shabaab and Hizbul Islam.
FIGHTING NEAR KENYA BORDER
In a separate incident on Saturday, fighting between Al Shabaab and Hizbul Islam fighters near Dhobley close to the Kenyan border killed six people.
I have seen dead people near Dhobley, two young men, Al Shabaab fighters. Also there are another four from the other side, said a resident who asked not to be named for security reasons.
Residents said Al Shabaab fighters had dug trenches in the town in what appeared to be defence lines against possible attacks from Kenya.
Kenya closed its border with Somalia in 2007 and has boosted patrols in recent months.