A female suicide bomber detonated as a minibus full of foreigners in Kabul stopped to refuel on the major road leading to the airport, killing around 12 people, according to reports.
Afghan militant group Hezb-e-Islami, which claimed responsibility for the blast, said it was in response to the film 'Innocence of Muslims', which makes out the Prophet Muhammad to be a womaniser and a child molester.
The group's spokesman Zubair Sediqqi said: "A woman wearing a suicide vest blew herself up in response to the anti-Islam video."
Teacher Abdullah Shah told the AP he was waiting for a bus to go to work, when he saw a small white sedan ram into the minibus. The car was packed with explosives.
"The explosion was so powerful and loud that I could not hear anything for 10 minutes."
A senior counter terrorism official in Kabul told the BBC: ''We can confirm that the suicide attack was carried out by a female suicide attacker. She is either a young girl or a woman.''
Reports suggested the foreigners on the bus worked at the airport, possibly for an international courier company.
General Muhammad Dawod Amin, a deputy for Kabul's police chief told The Guardian: "The target was a minivan carrying employees of a foreign company who had a contract with Americans.
"The seven foreigners killed were Russians and South Africans."
Police said three Afghans were also caught up in the blast.
Nato has announced it will restrict joint operations with Afghan forces, citing a recent rise in insider attacks, so-called 'green on blue' attacks have been responsible for 51 deaths in 2012.
The BBC reported that joint operations will now only be carried out when several hundred troops are involved in large scale operations.