"The Shebab mujahideen are urging people of Somalia to show their love for Islam and particularly to our Prophet Mohammed by making attacks against the West," Shebab spokesman Ali Mohamud Rage told AFP Saturday by telephone, without specifying any targets.
"The unprovoked attacks against Prophet Mohammed are not initiated by media houses and movie makers but they are clear instructions by Western governments," he said. "There should be great sacrifices when your country is under occupation and your religion is also under siege."
On Friday protesters burnt a US flag at a rally in Bulloburte, a town under Shebab control in central Somalia.
Since August last year, the Shebab have been forced out of Mogadishu and their other main strongholds in the south and centre of the country by Kenyan, Ethiopian and African Union soldiers backed by Somalia's weak pro-government military.
But they still control vast portions of central and southern Somalia.
On Friday and Saturday in Mogadishu, a handful of people staged peaceful demonstrations chanting slogans that criticised the movie "Innocence of Muslims", a low-budget production that depicts the Prophet Mohammed as a thuggish deviant in clips released online.
Abdullahi Sheikh Osman, a respected spiritual leader in Mogadishu, came on Saturday to talk to the protesters. "Don't kill innocent people for something they have not done," he urged Muslims. "The man who made the nasty film is the Al-Qaeda of Christians. If Muslims make havoc, then they are rewarding the crazy man," he told AFP.
"The person who made the filthy movie is not a religious person, but a reckless individual who dislikes harmony among people of different religious beliefs," he added.
The man apparently behind the film, 55-year-old Nakoula Bassily Nakoula, is a US-based Egyptian Copt who US officials said Friday was a fraudster who may have violated his parole.