Afghan authorities say a sixth person was also killed in the assault.
Burbridge said in a statement on Thursday that the “next of kin have been informed and our thoughts at this difficult time are with the loved ones of those who have died and been injured, and our brave team in Afghanistan who have lost colleagues and friends.”
The attack involved a suicide bomber ramming his explosive-packed truck into the gate of the G4S compound in Kabul, followed by an hours-long gunbattle with insurgents armed with grenades and automatic rifles.
The Taliban, who claimed responsibility for the attack, say it was retaliation for a U.S. airstrike in southern Helmand hours earlier on Wednesday that killed 30 people, many of them civilians.
Afghan officials have revised the number of casualties from a deadly Taliban attack the day before on the Kabul offices of a Britain-based security company to six people killed.
Earlier reports said the assault left 10 dead but Afghanistan’s public health ministry spokesman Wahid Majroh said on Thursday that four of the dead were attackers.
He says 23 people were wounded but didn’t identify any of the casualties. A suicide bomber detonated his explosives on Wednesday as other insurgents battled with Afghan forces near the security company called G4S.
The Taliban say the attack was revenge for a U.S. airstrike hours earlier in southern Afghanistan that killed 30 people, many of them civilians, including children.
Taliban spokesman Zabihullah Mujahid claims all 10 dead are foreigners. Insurgents often exaggerate their claims.