Kenyan President Uhuru Kenyatta has said that a siege by suspected militants in Nairobi is over and all the attackers have been "eliminated".

Gunmen attacked the compound in the Westlands district of Kenya's capital 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. It is not clear how many attackers there were.

The complex houses the DusitD2 hotel as well as offices.

In a TV address to the nation, Mr Kenyatta said 14 people had been killed but 700 others were safely evacuated from the complex.

However, the Kenyan Red Cross put the number of dead at 24.

A US citizen is among the dead, the US State Department said, and a British citizen was also feared killed.

"I can now confirm that... the security operation at Dusit is over and all terrorists have been eliminated," the Kenyan president said.

"We will seek out every person that was involved in the funding, planning and execution of this heinous act," he added, vowing to pursue them "relentlessly".

"We are a country governed by laws, rules and regulations - a country that embraces peaceful coexistence... I must also state that we are also a nation that never forgets those who hurt our children."