One witness told the AFP that the bomb went off alongside a busy road and that it left many people dead.
At least 20 people have been killed and several others wounded in a massive vehicle bomb attack outside a hotel in Somalia's capital, Mogadishu, police said, with officials fearing many casualties from the unusually large explosion.
Capt. Mohamed Hussein says the blast occurred Saturday as security forces were trailing the truck that had raised suspicions.
There was no immediate claim of responsibility, but the Al-Qaeda aligned Shabaab carries out frequent suicide bombings in the capital and elsewhere as it fights to overthrow the internationally-backed government.
The explosion was followed by gunfire between security forces and armed men around and inside the popular Safari Hotel. "I saw several dead bodies strewn about but could not count them", said witness Ismail Yusuf.
CBC News reported that the attack targeted a hotel on the central street.
Emergency services and ambulances arrived at the scene.
Witnesses told the BBC they believed dozens of people were dead. "And economically, I think this is the worst ever in Mogadishu in a single day".
The blast, which also wounded at least 15 people, occurred two days after the head of the U.S. Africa Command was in town to meet with Somalia's president.
However, the militants continue to control rural areas and launch attacks on military, government and civilian targets in Somalia, as well as terrorist raids in neighbouring Kenya.