At least 18 people were wounded in the attack, which comes three days after 14 people -- mostly foreigners -- were killed in a Taliban assault on a Kabul guest house that trapped dozens attending a concert.
The suicide bomber targeted the foreign convoy, which included two vehicles of the European Union Police Mission in Afghanistan (EUPOL), during the morning rush hour near Kabul airport.
"The target of the attacker was the foreign forces convoy. So far we have two women dead, 18 others wounded, all of them civilians," he said, adding that three children were among those wounded.
A foreigner working with EUPOL was also killed, a spokesman for the unit told AFP, with the London foreign office confirming that he was a British national.
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"All we can say at this moment is that two of EUPOL's vehicles were there at the time of the attack. The one killed inside a vehicle was a foreigner who worked for EUPOL," said Aziz Basam, senior press officer.
An AFP photographer at the scene saw troops hauling away the body of a person in military-style uniform, pulled out from the twisted wreck of a badly damaged sedan.
Taliban insurgents, who have stepped up attacks on foreign targets after launching their spring offensive late last month, claimed responsibility for the car bombing.
"A suicide attack was carried out on foreign forces near the gate of Kabul airport," spokesman Zabihullah Mujahid said on Twitter.
On Friday the militant group justified its targeting of foreigners, saying that people from "invading countries" do not count as civilians.