Two Britons and a child of another UK national were killed in the twin bombings at the Kabul airport, Foreign Secretary Dominic Raab said.
"I was deeply saddened to learn that two British nationals and the child of another British national were killed by yesterday's terror attack, with two more injured," Raab said in a statement on Friday.
Two suicide bomb attacks rocked the Kabul airport in the Afghan capital on Thursday, killing at least 103 people, including 13 US service members, and injuring 158 others.
The Islamic State (IS) terror group has claimed responsibility for the deadly attack, saying it was targeting "translators and collaborators with the American army".
"These were innocent people and it is a tragedy that as they sought to bring their loved ones to safety in the UK they were murdered by cowardly terrorists," the Foreign Secretary said.
Britain's evacuation operation at the Kabul airport has "a matter of hours" left and no more people will be called forward, Defence Secretary Ben Wallace said on Friday.
Prime Minister Boris Johnson said on Thursday that around 15,000 people, the "overwhelming majority" of those eligible to come to the UK, had been evacuated by British troops.
These include Afghans who supported British troops in Afghanistan and British passport holders.
Only four days remain for US-led forces to evacuate from Afghanistan, after Johnson and leaders of other American allies failed to persuade US President Joe Biden to extend the August 31 evacuation deadline during a Group of Seven virtual summit earlier this week.