'White Widow' lived among South Africans

A British woman thought to be linked to the Nairobi mall attacks used an assumed South African identity to take out bank loans and rent property in Johannesburg, say local media reports.

Samantha Lewthwaite - wanted by Kenyan police for alleged involvement in a separate terror plot - used the known alias Natalie Faye Webb to rent at least three properties and run up debts of $8600 ($A9311), according to the eNews Channel Africa (eNCA).

The 29-year-old Muslim convert - nicknamed the "White Widow" because her husband was among the 2005 London suicide bombers - signed rental leases around Johannesburg, but it was unclear whether she lived at any of the premises.

According to credit records released by eNCA, she was listed as living in the city's predominantly South Asian neighbourhood of Mayfair for four years.

Kenya's foreign minister has said a British woman was among the Islamist attackers who shot dead dozens of people at a Nairobi shopping mall from Saturday.

President Uhuru Kenyatta later said the reports could not be confirmed.

But Kenyan authorities issued a wanted notice for Lewthwaite after she entered the country from Tanzania's northeastern Lunga and Namanga border posts in February and August 2011 using a South African passport in the name of Webb.

Two months later South African clothing stores signalled debt defaults worth almost $2700.

In August 2012 a Johannesburg court issued an order against her for defaulting on $2800 debt with South Africa's First Rand Bank.

Lewthwaite was married to Germaine Lindsay, one of four suicide bombers who attacked the London transport network in July 2005, killing 52 people.

A local terror expert and academic said earlier this week that she regularly travels to South Africa and stayed in South Asian suburbs of Johannesburg earlier this year.

However residents either denied Lewthwaite had lived at the cited addresses or could not remember having seen her.