“A suicide bomber walked into the meeting hall and blew up himself," a relative of one of the victims told Reuters on Wednesday, Presstv Reported.
Mohamed Abdullahi added that his cousin and the mayor of Mogadishu were among the local officials hurt in the attack.
Shopkeeper Mohamed Osman said the area was packed with ambulances after the explosion.
However, a security official said
"The blast occurred inside but we are not sure what exactly caused it, some reports we are getting indicate it was caused by a suicide bomber... and there are casualties," said al Mahdi Abdirahman.
He did not give further details on the wounded.
"The blast was very heavy, and I saw people, fleeing some with shrapnel wounds outside the Banadir administration headquarters," said witness Mohamud Shariif, referring to the regional government offices.
There were no immediate details about casualty numbers and no one has yet claimed responsibility for the attack, which bore the hallmarks of the al-Qaeda-linked al Shabaab Takfiri militant group.
Al-Shabaab was forced out of Mogadishu with the help of African Union forces in 2011. However, it still wields control in large parts of the countryside, and every now and then carries out deadly attacks against government, military, and civilian targets in the capital as well as regional towns.
Mogadishu was on Monday struck by a car bomb that left 17 dead and more than two dozen wounded.
Al-Shabaab, which has fought successive Somali governments as well as neighboring governments in Kenya and Uganda, claimed responsibility for Monday's attack near a busy security checkpoint outside the Afrik Hotel.
The Monday attack came just over a week after 26 people were killed and 56 injured in a 12-hour attack by al-Shabaab on a popular hotel in the southern Somali port city of Kismayo.
In that attack, a bomber rammed a vehicle loaded with explosives into the Medina hotel before several heavily armed gunmen forced their way inside, shooting as they went.