About four gunmen armed with rifles and grenades drove to the complex at around 3 pm local time and staged a deadly attack, leaving a trail of destruction.

"We have secured all the buildings that had been affected. The situation is under control and the country is safe. Terrorism will never defeat us. We will not surrender or bend," Matiang'i said.

He did not say how many people were killed or injured in the attack, but there were reports that 15 people were killed.

The US State Department has confirmed that one of the victims was an American citizen.

Al-Shabab, a Somalia-based extremist group, has claimed responsibility for the attack.