Six Britons are now believed to have been killed in an attack at a Nairobi shopping mall staged by Islamist militants, defence secretary Philip Hammond said on Monday.
"Our current best estimate is we now have six British nationals who have died in this incident," he said after a meeting
of the government's emergency committee chaired by Prime Minister David Cameron.
Three Britons and a dual British-Australian national had earlier been confirmed as among at least 62 people killed in the brutal assault at the Westgate mall in the Kenyan capital.
Hammond said another British victim had been confirmed and officials were awaiting final confirmation on the sixth.
"Of the additional two, one is confirmed and another one we believe to be a British national and we are awaiting final confirmation," he said.
"But we are pretty certain we now have six British nationals who have died."
Referring to the ongoing situation at the mall, where the attack began on Saturday, he said: "It is possible that we will discover further British nationals once the building is fully secured."
British businessman Louis Bawa said his eight-year-old daughter Jennah and wife Zahira were among the dead.
Bawa told the Daily Telegraph that "my heart just stopped" when he was asked to identify them from photographs taken of those killed at the mall.
"The people who did this, they are vigilantes, they are animals," he added.
"They are using religion as an excuse to kill people. Zahira and Jennah were Muslims, but these animals just shot them the same as all of the others."
British press also reported that architect Ross Langdon, who held joint UK and Australian citizenship, died along with his pregnant Dutch partner Elif Yavuz.
Samri Bhamra, from Leicester in central England, said that four members of his family had died while recording an episode of "Junior Masterchef" in the mall, the Times reported.
Cameron cut short a stay with Queen Elizabeth II at her private Balmoral estate in Scotland to return to London on Monday to chair the emergency response committee COBRA.
The committee had held one meeting without him on Monday morning.