NAIROBI, Jan. 15 (Xinhua) -- The Kenyan government said Tuesday security situation in the country is under control after an unknown number of terrorists attacked an upmarket hotel and office complex in the capital, Nairobi, and killed at least six people.

Fred Matiang'i, Cabinet Secretary for Interior and Coordination of National Government, said 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 on Tuesday evening.

"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 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.

Police said the gang arrived at the entrance of the DusitD2 hotel and alighted before one of them started to shoot aimlessly.

The gang first shot and seriously wounded two students who were walking out of the hostel.

The gunshots alerted police guarding the nearby Australian embassy. The officers rushed there and engaged the gunmen in a gunfight deflating the saloon car that they had.

It was at that point that one of the attackers lobbed a grenade at three cars that were parked at the main barrier, setting them on fire. They were burnt to ashes.

The terrorists then proceeded to the main hotel lobby where one of them detonated an explosive device he had on his body. His limb was blown out of the lobby to the main corridor about 40 meters away.

"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," vowed Matiang'i.

Joseph Boinnet, Inspector General of Police, said the terrorists began their onslaught by setting ablaze three vehicles at the I&M Bank parking lot before moving to the DusitD2 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 pointed out that 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 7 floors of the hotel building have been secured," said Boinnet.

Al-Shabab terrorist group claimed responsibility for the attack, saying its fighters conducted a terrorist attack in upmarket Kenya, killing 47 people inside the hotel.