At least six Afghan civilians have been killed in a suicide bomb attack in the capital, Kabul, officials say.The bomber blew up his vehicle next to a convoy of foreign armoured cars in the east of the city, police say. Two children were among those killed and at least 30 more people were injured. The Nato-led International Security Assistance Force (Isaf) in Afghanistan has confirmed that one of its convoys was hit. Government officials said those who died were bystanders. Smoke rose above the industrial district of Karta-e Naw, in the east of the city, after the powerful explosion. An explosives-filled Toyota Corolla was blown up beside two foreign military vehicles at around 08:00 (03:30 GMT), Kabul Police Chief Gen Salangi said. The force of the blast destroyed several houses and a wide area of the city has been cordoned off. Sirens could be heard afterwards as ambulances headed to the scene. The BBC's David Loyn in Kabul says harrowing images of the aftermath of the explosion have emerged, with badly burned bodies and an elderly man, his head seriously wounded. "I heard a terrible explosion and our whole building shook," a local resident told AFP news agency. An insurgent group linked to the Taliban, Hezb-e-Islami, told the BBC in a phone call that it carried out the attack. It is the first major blast in Kabul since March, when a suicide bomber blew himself up near the defence ministry, killing nine people. The latest attack comes during what has been a bloody month for Isaf in Afghanistan, with at least 15 foreign military personnel killed in separate incidents since the beginning of May. The Taliban announced a "Spring offensive" in April, saying it would target foreign military bases and diplomatic areas.