Sheikh Jama Abdusalam said such uprisings would rid the war-wracked country of a government that he accused of serving Western interests.
"I am urging the people to carry out Egyptian- and Tunisian-style uprisings in Somalia," Abdusalam told Alfurqaan Radio, a Shebab mouthpiece.
"It is good to take up such revolution against all governments that serve the interest of Western countries," he said. "We have to follow Muslims who are fighting for their dignity and religion in Tunisia and Egypt."
The Shebab control 80 percent of southern and central Somalia and their bloody onslaught against President Sharif Sheikh Ahmed's government has confined the administration to a few blocks in the capital Mogadishu.
Somalia's transitional government was formed in neighbouring Kenya in 2004 but has been unable to exert its authority across the country and survives under the protection of a contingent of African Union forces.
Another Shebab imam, Sheikh Abdulfatah Aweys Abu Hamsa, called for more attacks on African Union soldiers.
"There is a need for a wider jihad against the crusaders who came to support the transitional government," Alfurqaan Radio quoted him as saying.
"We need to follow those who are crushing dictators. We need to remove the so-called leader imposed on us by outsiders," he said.
Somalia has lacked an effective central government since the eruption of a civil war after the ouster of president Mohamed Siad Barre 20 years ago.
The current government's mandate is to expire in August.