The Islamist group which controls much of southern
Islamist leader Sheikh Sharif Sheikh Ahmed said khat was a bad influence. Many Somali men, especially gunmen, spend hours chewing it each day.
He also warned squatters to vacate public buildings they have occupied.
After 15 years of conflict, many ministries are full of people who have fled fighting in their home regions.
Eyewitnesses say one person was shot dead by Islamist fighters on Thursday following protests over khat shortages.
About 60 khat vendors burnt tires and threw stones in protest at shortages of the drug since a ban on flights to
"From today onwards we have banned khat in the areas we control," Mr Ahmed said.
"Dealers found in possession of khat will pay 7 million Somali shillings ($500) and the khat will be burned. This substance is badly influencing our people."
The Islamists have burned two big khat consignments flown in this week to make up for the lack of Kenyan khat.
There were six flights a week from
The BBC's Hassan Barise in
'Reconstruction'
Mr Ahmed's call for squatters to vacate government buildings is seen as an attempt to restore normality to the shattered nation.
"Such buildings would be part of
But some question where people could go to.
Shelters made from plastic sheets and pieces of cardboard have been erected in the grounds of many public buildings.
Offices, too, have been taken over, with several families sharing a single room, in which the windows and fittings have long since been broken or stolen.
The Islamists have taken control of most of southern
Many
In some parts of the country, Islamists have been closing public cinemas and, according to some residents, enforcing strict dress codes.
There are fears of a regional conflict starting in
Photo Caption
Somali fighter