Somali police Col. Mohammed Dahair said the evening explosion happened at a cafe near the seat of government. He could not immediately say how many others were wounded.

A second police official, Abdiwali Hassan, said three journalists were among those killed. He did not know if any prominent politicians were among the dead.

The attack was likely carried out by the militant group al-Shabab which has been fighting the Somali government for nearly five years. Africa Union forces pushed the al-Qaida affiliated group out of Mogadishu in August 2011 but the militants have continued to carry out suicide attacks in the capital.

The U.N. secretary-general's special representative to Somalia condemned the attack, which follows Sunday's inauguration of President Hassan Skeikh Mohamud.

"I strongly condemn this cowardly and senseless attack. These acts of terrorism cannot reverse the recent achievements that Somalia has witnessed - such incidents can only reinforce the determination of the Somali people to reject violence and engage in peaceful resolution of conflict," said Augustine P. Mahiga, head of the U.N. Political Office for Somalia.

The election of Mohamud marked the end of an eight-year U.N.-backed political transition period, which also saw the recent election of a parliament and the adoption of a provisional constitution.

"This attack coming at a time when the people have resoundingly welcomed a popular process towards attaining more legitimate and representative institutions is an affront to the will of the Somali people and an attack on the return of normalcy to Somalia," Mahiga said. "We will not let the hard-won momentum towards stability be affected by such events."