Afghan insurgent group Hezb-e-Islami claimed responsibility for a suicide attack on a minibus that killed 12 people, including nine foreigners, near Kabul airport and said it was launched in retaliation for a film mocking the Prophet Mohammad.
"A woman wearing a suicide vest blew herself up in response to the anti-Islam video," said Zubair Sediqqi, a spokesman for the militant faction, which does not usually carry out such attacks.
The attack underscored growing anger in Afghanistan over the film, which has enraged much of the Muslim world and led to the killing last week of the US ambassador to Libya and three other Americans.
Thousands of protesters clashed with police in the Afghan capital on Monday, burning cars and hurling rocks at security forces in the worst outbreak of violence since February rioting over the inadvertent burning of Korans by US soldiers.
The suicide attack was the first in Kabul involving a woman and the foreigners killed were mostly Russian and South African pilots working for an international courier company, senior police sources said.
The toll was the highest on foreigners in the city since last April when an Afghan air force pilot gunned down eight US military flight instructors and an American civilian adviser after an argument at Kabul International Airport.
Hezb-e-Islami, which means Islamic Party, is a radical militant group which shares some of the Taliban's anti-foreigner, anti-government aims.