At least three police officers died when a car bomb exploded outside a tea shop in the Somali capital Mogadishu on Wednesday, police said.

"There was a car bomb explosion near the police transport headquarters early this morning," said Mogadishu police commissioner Ali Hersi Barre, adding that the suspected driver was in police custody.

The three officers were drinking tea when the blast occurred and the man driving the car that exploded was "seriously wounded," said the commissioner.

He added that a three-wheeled tuk-tuk taxi loaded with explosives also blew up this morning, after being seized by police last night, but said there were no casualties from the blast.

"One of three men who drove the three-wheeler was arrested and two others have escaped," Ali said.

The tea shop where the explosion occurred is popular with police based at the nearby transport headquarters in northern Mogadishu. There were no civilian casualties reported.

No group has so far claimed the attack but Al-Qaeda insurgents, the Shebab, which is fighting to overthrow the internationally backed government frequently deploys car bombs.

The Shebab was chased out of Mogadishu in 2011 but remains a dangerous threat in both Somalia and neighbouring Kenya where it carries out regular attacks.

On Saturday, the US said it carried out air strikes on a Shebab training camp, claiming to have killed at least 140 fighters.