A joint Australian-British architect and his heavily pregnant Dutch wife were named by friends and media Monday as among those killed in the attack on an upmarket Nairobi shopping mall.

Ross Langdon, 33, and his wife Elif Yavuz were among 69 people known to have died in the attack which began on Saturday when Islamist gunmen armed with rifles and grenades stormed the city's Westgate mall.

Friends and colleagues used blogs and the couple's social media profiles to pay tribute to the pair, who were due to become parents for the first time in two weeks.

"Such tragic news about beautiful Ross Langdon & his pregnant partner Elif Yavuz in Nairobi. Very special souls," wrote Sydney designer Liane Rossler on Twitter.

"Horrible news that Ross Langdon and his wife were killed in the Nairobi attacks," added Sydney architect Marcus Trimble.

Langdon, a specialist in socially sustainable tourism infrastructure in environmentally sensitive locations, grew up in Tasmania but worked on projects around the world, including in London, Sydney, Norway, Uganda and Rwanda.

Friends said he donated much of his time in Africa for free.

"He was a colleague and friend who went out into the world as an architect doing wondrous things," sculptor Peter Adams wrote on his blog.

"He designed -- pro bono -- an AIDS hospital in Kenya. In Uganda he designed and supervised a unique eco-village employing only local labour. There is much, much more."

The pair were expecting their first child in two weeks, and Adams said malaria specialist Yavuz, 33, had recently met Bill Clinton through her work with the Gates Foundation in Kenya.

A photograph recently posted on her Facebook page showed a heavily pregnant Yavuz shaking hands with the former American president, the Age newspaper reported.

"Both had dedicated their lives to working for a peaceful world. Both had so much to offer," Adams added.

Langdon is believed to be one of the three British nationals whom the British Foreign Office said were confirmed killed.

Britain has yet to name the three until their next of kin have been informed.

In 2012 Langdon gave a talk at a TED conference in the Polish city of Krakow about his sustainable projects in Uganda. He said he was inspired by a childhood in a rural backwater of Tasmania.

"We milked our own cows, worked the land and grew vegetables and fruit that we lived off," he recalled, in a video of the talk available online.

Dutch-born Yavuz held a PhD in public health policy at Harvard, the Herald Sun newspaper reported.

"They didn't want to know if the baby was a boy or a girl, so they had chosen names for both sexes," a friend who visited the couple in Nairobi in the past week wrote on Yavuz's Facebook page, the newspaper reported.