A US businessman who reportedly survived the 11 September World Trade Centre terror attack in 2001 is among at least 14 people to have been killed in by suspected militants in Nairobi.

Jason Spindler, founder and managing director of I-Dev International, a business development firm based in the Kenyan capital, was killed in the attack on Tuesday, his mother told NBC.

The US Department of State confirmed an American had died in the attack but did not provide further details.

The Somalia-based militant group al-Shabab claimed responsibility for the attack.

Sarah Spindler told the the US broadcaster: "We all miss him so much.

"And it's so sad that such a bright young person is taken away by terrorism.

"[He] was trying to make positive change in the third world in emerging markets."

Friends and family paid tribute to Mr Spindler on social media.

A Facebook post from a family member said the "survivor of 9/11" would be dearly missed.

"You are and will always be an amazing son, brother and uncle," the post read.

The United States Ambassador to Kenya, Bob Godec, commended the Kenyan security services for their "speed and courage... in ending the 15 January terrorist attack at the Dusit2D Hotel complex in Nairobi".

"It is with great sadness that we confirm one American citizen was killed. We are assisting the family of the victim and other US citizens who were affected," he said.

"We offer our deepest condolences to the families and friends of all those who were killed and we wish a quick, full recovery to all those injured." (BBC)