Al Qaeda-linked al Shabaab claimed responsibility for the attack.
"A suicide bomber blew himself up in a restaurant," police chief Hussein Osman told Reuters from Baldwin.
Police and residents said the blast, which occurred Sunday afternoon, was near the headquarters of the provincial governor of Hiran, which was holding a meeting inside.
"We stand behind the attack at the headquarters of the governor of Hiran, there are dead and wounded, we have targeted the staff of the Hiran administration," said al-Shabaab military spokesman Abdul Aziz Abu Musab.
"The bomber, who was wearing an explosive vest inside the restaurant and blew himself up, was going to attend a meeting in the governor's office when the explosion occurred," one of the elders said.