Samantha Lewthwaite, 28, who is wanted for possessing explosives and conspiring to make bombs, has been on the run with her three children since she escaped a swoop on terrorist suspects in Mombasa in December.
She has now been linked to last Sunday’s attack on the Jericho Beer Garden in the Kenyan city.
Alex Momanyi, 26, whose cousin and friend died in the attack, said: ‘I was outside taking a call when the place was blown apart.
‘Three cars drove off, but a few minutes later one of them, a white Toyota station wagon, returned and a woman in Muslim robes ran from some nearby bushes and got into it.’
A police source said: ‘The sighting of a Muslim woman in a noisy place where people were drinking is highly significant, and we believe Lewthwaite could be involved.
‘She has emerged as a woman capable of masterminding this sort of act and being actively involved.
She has been at large for months and may think she is invincible after merging into the Muslim community.’
Lewthwaite, of Aylesbury, Buckinghamshire, converted to Islam in her teens. She denounced her bomber husband Jermaine Lindsay after he killed 26 people in a suicide attack on London’s Piccadilly Line in 2005.
But she left England to travel abroad and has been linked to Somalia’s al-Shabaab terror group. She is also believed to have set up terrorist cells with Briton Jermaine Grant, who is due to go on trial in Kenya next month accused of conspiring to carry out bomb attacks.
A Scotland Yard spokesman said yesterday: ‘We cannot not reveal details of the team’s trips to Kenya for security reasons.’