By Godfrey Kampamba
In a TV address to the nation, President Kenyatta said 14 people had been killed but 700 others were safely evacuated from the complex. The Kenyan Red Cross put the number of dead at 24.
Gunmen attacked the compound in the Westlands district of Kenya's capital Nairobi on Tuesday, killing at least 14 people.
Officials originally announced the end of the siege hours after it began, but gunfire and explosions were heard again early on Wednesday.
The Somalia-based militant group al-Shabab said it was behind the attack in the complex that houses the DusitD2 hotel as well as offices.
It is not clear how many attackers there were. Along with Kenyans, those dead include nationals from other countries.