The Al-Shabab militant group has reportedly claimed responsibility for the attack.
"A suicide car bomb rammed into the centre of the controversial cleric called Abdiweli. Now the militants are inside and firing at those inside," an elder in the town of Galkayo Farah Nur was quote as saying by Reuters.
Al-Shabab, which has sworn allegiance to the Al-Qaeda terror group, has been staging numerous attacks across the country in an attempt to impose a radical version of Sharia law.
Somalia has been engulfed in violence since the eruption of a civil war between clan-based armed factions in the early 1990s.