A suicide bomber rammed a car packed with explosives into a mini-bus carrying foreign aviation workers to the airport in the Afghan capital early Tuesday, killing at least 12 people including eight South Africans.

A militant group claimed the attack aimed to avenge an anti-Islam film that is highly provocative and offensive to Muslims.

The powerful early morning blast was the first to target Kabul since a video clip of the film was posted on the internet last week, sparking angry protests across the Muslim world including in Afghanistan. It was also the second — and deadliest — attack in Afghanistan that militants have said they carried out as revenge strikes in response to the film.

Haroon Zarghoon, a spokesman for the Islamist militant group Hizb-i-Islami, claimed responsibility for the dawn attack in a telephone call to The Associated Press. He said it was carried out by a 22-year-old woman named Fatima. Suicide bombings carried out by women are extremely rare in Afghanistan, and few if any women drive cars.

"The anti-Islam film hurt our religious sentiments and we cannot tolerate it," Zarghoon said. He said the 22-year-old Fatima volunteered to be the suicide bomber.

"There had been several young men who wanted to take revenge but Fatima also volunteered and we wanted to give a chance to a girl for the attack to tell the world we cannot ignore any anti-Islam attack."

Zarghoon warned of more attacks against foreigners working for NATO and said the group had been seeking targets. The bombing was a worrisome escalation of violence in the capital, where most attacks are usually blamed on the Haqqani network — a Pakistan-based militant group affiliated with the Taliban and al-Qaeda.

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Twelve people died in a suicide bomb attack in Kabul. (Google)

"Foreign troops are fighting against Afghans and foreign civilians are tasked to spy for them. They all are our enemy and will be our target," Zarghoon told The AP, speaking from an unknown location.

Eight of the dead were South Africans believed to be working for an aviation company based at Rand Airport in Johannesburg, South Africa's International Affairs Ministry spokesman Nelson Kgwete said.

Afghan Interior Ministry spokesman Sediq Sediqqi said that four Afghans also were killed and another 11 Afghan civilians were wounded. He said tests were underway to determine whether the suicide bomber was a woman.

Tuesday's blast came a day after hundreds of Afghans burned cars and threw rocks at a U.S. military base in the capital in a demonstration against the anti-Islam film. One police vehicle was burned by the mob before they finally dispersed around midday Monday.

Mini-bus hurled 50 metres

Kabul police chief Gen. Mohammad Ayub Salangi said Tuesday's explosion took place near an avenue northwest of the city centre near Kabul International Airport. The blast was so powerful it hurled the mini-bus at least 50 metres.

An eyewitness at the scene said he was waiting at a bus stop along the road when he saw a small white sedan ram into the mini-bus.

"The explosion was so powerful and loud that I could not hear anything for 10 minutes," said Abdullah Shah, a teacher. "It was early and there wasn't much traffic or there would have been many more casualties."

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An Afghan protester shouts slogans near burning tires during a demonstration Monday in Kabul over an anti-Islam film released on the internet. (Omar Sobhani/Reuters)

Hizb-i-Islami, a radical Islamist militia with thousands of fighters and followers across northern and eastern Afghanistan, is headed by 65-year-old former warlord Gubuddin Hekmatyar, a former Afghan prime minister and one-time U.S. ally now listed as a terrorist by Washington.

The group has recently been seeking to participate in a so-far fruitless peace and reconciliation effort led by the Afghan president. Its more moderate parts are thought to have close ties to the Karzai administration and offered a peace plan that called for a broad-based government.

Hekmatyar and was one of the primary recipients of military assistance from the United States and Pakistan throughout the 1980s and early 1990s when he was helping fight the Soviets.

A moderate branch of the group operates as a political party in Afghanistan and has representatives in the Afghan government, including cabinet ministers.

The political arm of Hizb-i-Islami has denounced Hekmatyar and his violence but it is not clear whether they have completely severed ties. Karzai has worked to court the group's political wing in a move to encourage them into peace talks with the government.

British base attacked

The Taliban have also threatened to increase their attacks against foreign targets as revenge for the controversial film. Taliban fighters last week attacked a large British base in southern Afghanistan, killing two U.S. marines and destroying six fighter jets. NATO forces killed 14 insurgents and captured another who participated in the attack.

Zarghoon, the spokesman for Hizb-i-Islami, said recent events such as the mistaken bombing by NATO that killed eight women and girls who had gone out before dawn to gather firewood in remote eastern Laghman province, a traditional Hizb-i-Islami stronghold, has soured the organization's desire for reconciliation talks.

"Americans have not taken any serious steps for peace," he said. "They killed civilians in Laghman two days ago who had gone to cut wood. When the Americans show they are serious about talks and a solution, we will talk peace then."

The U.S.-led coalition acknowledged that civilians had been killed and expressed its regret over the airstrike. It insisted known insurgents had been the target.