‘White widow’ Samantha Lewthwaite may have been killed during the Nairobi siege.
As attempts to flush the remaining militants out of a Kenyan shopping centre continued, officials said three Islamist extremists had died during attempts to free their hostages.
Insiders said one was a white woman â€“ adding weight to the theory that Lewthwaite, the fugitive widow of 7/7 bomber Jermaine Lindsay, was behind the attack that has left 62 dead and 170 injured.
Downing Street said at least six of the dead are British and warned there was â€˜potential for further bad newsâ€™.
A report from the Reuters news agency said three sources â€“ one intelligence officer and two soldiers â€“ had confirmed that a white woman was among the fallen terrorists.
Police are exploring whether she could be a hostage dressed in one of the terroristâ€™s clothes, but the Foreign Office is also examining Muslim convert Lewthwaiteâ€™s links to the massacre.
The 29-year-old mother of four, from the Home Counties, is now a leading figure in Al Shabaab â€“ the terror group that has claimed responsibility for the killings in the Israeli-owned Westgate shopping centre.
Police believe she is the one of the groupâ€™s main financiers and bomb-making tutors. However, sources admit they still do not know the full extent of her involvement in the attack in Nairobi.