The government figure for the number of Britons killed in the Nairobi shopping mall attack has been reduced from six to five.

The Foreign Office said one of the victims previously thought to have been a UK national was Kenyan.

However, a spokeswoman warned that the casualty figure could still rise further as the authorities continue to comb the scene.

"We can now confirm that on present information five British nationals have been killed in the recent terror attacks in Nairobi," she said.

"One individual previously thought to be British is a Kenyan national. Our thoughts are with his family and with the friends and family of all of those who have died during this difficult time.

"We have no information at this time that any further British nationals have been killed, although we cannot rule out the potential for further British casualties and we continue to stay in close contact with the Kenyan authorities as their investigations continue."

The death toll from the attack by al-Shabab militants on the Westgate shopping mall is expected to rise from the current level of 67, with more than 60 people apparently yet to be accounted for.

Somali president Hassan Sheikh Mohamoud warned such attacks may become more frequent as al-Shabab attempts to reassert its dwindling power base.

He told Channel 4 News: "Some people sometimes mix the issues that Shabab want an Islamic state in Somalia - that's not true. Shabab want a unified (one) state all over the world.

"They do not believe in borders, they do not believe in sovereignty, so their theme is global, it's not even regional."

He warned: "They may do this act again and again.

"The act is of a dying organisation. You see Shabab now they control remote parts of Somalia, where they are still using as their training territory, where they are still using as a bomb factory, where they still have in the training centre special units that brainwash the young people from within Somalia, out of Somalia. So, these types of things will continue."

The full "forensic audit" of the Nairobi shopping mall terror attack will take at least seven days to complete, the country's interior minister has said.

Joseph Ole Lenku said it was still not known whether there were any Britons or Americans among the al Qaida-linked militants or whether any of them was a woman.

"In our previous briefings we indicated that there was no indication to suggest that there is a woman terrorist but going forward we are all hearing possibilities and information - including volunteers from the public," he told reporters.

"We want to again request you to allow the forensic experts to determine whether that is true."

The persistent suggestion that a woman was involved has led to speculation that it could be the British terrorist suspect Samantha Lewthwaite - who was married to the July 7 bomber Jermaine Lindsay.

Dubbed the "White Widow", Lewthwaite is known to be in East Africa and is wanted by Kenyan police over alleged links to a terrorist cell that planned to bomb the country's coastal resorts.

Mr Lenku said the forensic teams - including experts from the US, Israel, Germany, Canada and Interpol - were examining fingerprint, DNA and ballistics evidence in the hunt for clues.

The Kenyan authorities have said that 61 civilians and six members of the Kenyan security forces were known to have died during the stand-off. Five terrorists were also killed while 10 suspects remain in custody in relation to the incident.

A British businessman paid tribute to his wife who died in the attack by the Somali Islamist group which ended on Tuesday, after four days.

Niall Saville, an economic development consultant from Lincolnshire who was shot in the shoulder in the siege, has been left "devastated and heartbroken" after Moon Hee Kang died from wounds received in a grenade explosion.