As per latest update on the attack, the security forces were battling the attackers till the morning.
A Somalia based Islamic extremist group Al-Shabab, which carried out the 2013 Westgate Mall attack, claimed the responsibility, agencies reported.
The lush complex witnessed a horrifying scene with blood and shattered glass, burnt vehicles, thick black smoke , people running and screaming while some ducking to save their lives.
Kenyan police chief Joseph Boinnet said in a statement on television: “We can now confirm that this criminal activity commenced at about three o'clock [1200 GMT] in a coordinated fashion and began at I&M Bank with an explosion that targeted three vehicles in the parking lot, and a suicide explosion in the foyer of Dusit hotel,” news agency AFP reported.
“We have 15 people dead as of now and that includes foreigners. You will be given more details on all this and even the nationalities by our seniors," a police source told AFP on condition of anonymity.
Explosions and gunshots could be heard at 11 pm about eight hours after the attack began, reports said.
"There was a bomb, there is a lot of gunfire," whispered a man working in the offices in the Dusit Hotel compound, asking not to be named
The numbers of attackers are not yet clear, but witnesses said they saw two men shooting.
However, a Kenyan police officer who spoke on condition of anonymity because he was not authorized to talk to the media said that bodies were seen in restaurants downstairs and in offices upstairs, but "there was no time to count the dead, Associated Press reported.
The attack came a day after a magistrate ruled that three men must stand trial on charges they were involved in the Westgate Mall siege.