NAIROBI, Jan. 16 (Xinhua) -- More people were evacuated early Wednesday from the site of a terror attack at an upmarket hotel and office complex in the Kenyan capital, Nairobi, following fresh blasts and gunshots, several hours after officials said that the situation was under control.

Live broadcast by local NTV station showed one of the evacuees saying people holed up in places like toilets for hours before police came to their rescue.

Cabinet Secretary for Interior and Coordination of National Government Fred Matiang'i said late Tuesday that security teams have evacuated scores of Kenyans and other nationalities from the buildings after a nine-hour operation.

"We are now in the final stages of mopping up the area and securing evidence and documenting the consequences of this unfortunate event," he told journalists.

"I can now report that the country is now secure and that the nation remains calm, that Kenyans and all our visitors are now safe," he added.

The DusitD2 complex, which houses several multi-national offices and a hotel, is located in the leafy Riverside area of Westlands, Nairobi.

About four gunmen armed with rifles and grenades drove to the 14 Riverside Drive at around 3 p.m. 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 U.S. State Department has confirmed that one of the victims was an American citizen.

Joseph Boinnet, Inspector General of Police, said earlier that the terrorists began their onslaught by setting ablaze three vehicles at the I&M Bank parking lot before moving to the Dusit D2 complex.

At the entrance of the hotel, Boinnet said the assailants carried out a suicide explosion, injuring several people.

"This criminal activity commenced at about 3 o'clock in a coordinated fashion that began with an attack at I&M Bank with an explosion that targeted three vehicles on the parking lot and suicide explosion in the foyer at Dusit hotel where a number of guests suffered severe injuries," said Boinnet.

He said a multi-agency special security team had made progress to regain control of the hotel where the gunmen are holed up.

"Owing to swift and targeted response by our security agencies, the situation has been largely contained and six out of the seven floors of the hotel building have been secured," said Boinnet.

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