Kenyan President Uhuru Kenyatta said Wednesday that all Islamists who had stormed an upmarket hotel complex had been "eliminated" after an almost 20-hour siege that left at least 14 dead.

"I can confirm that... the security operation at Dusit complex is over and all the terrorists eliminated," Kenyatta said in a televised address to the nation.

"As of this moment, we have confirmation that 14 innocent lives were lost to the... terrorists, with others injured."

Police sources and a mortuary official had previously reported 15 dead.

Kenyatta said 700 civilians had been rescued throughout the siege, but did not clarify if people were still hiding in the complex.

It was not immediately clear how many attackers there were in total.

CCTV footage broadcast on local media showed four black-clad, heavily armed men entering the complex on Tuesday afternoon.

At least one of them blew himself up at the start of the attack.

A police source said two attackers had been shot dead Wednesday morning after a prolonged shootout.

"The two have red bandanas tied around their forehead and bullets strapped around their chest with several magazines each," the senior police officer said.

"Each had an AK47 which has been secured."