A suicide bomber drove his explosives-packed Toyota Corolla into armoured SUVs carrying Nato troops and civilians through Kabul, killing six passengers and nine Afghan civilian passersby, two of them children.

The attack was the deadliest in Kabul this year, ripping through morning traffic in the western side of the Afghan capital at the peak of the morning rush hour.

The blast was so loud it echoed across the city, and a huge plume of smoke rose from the debris as helicopters, US military vehicles and Afghan security services rushed to the site. Two Nato troops and four contractors were killed in the attack.

“Around 8 o’clock this morning two vehicles belonging to foreign advisers were bombed by a Corolla. They were badly damaged, along with 10 civilian cars, and another 20 vehicles in the area were lightly damaged,” said the Kabul police chief, Ayoub Salangi.

The remains of one of the Nato vehicles, so twisted and lacerated it would have been impossible for anyone inside to survive, was still lying at the site of the attack when journalists were given permission to approach the scene several hours after the blast.

The bodies of Afghan victims were so badly burned they could not be identified, said Qabir Amiri, spokesman for the city’s hospitals. The toll continued to mount through the day.

“There were nine (Afghan) civilians killed, two of them children. Another 39 civilians were injured,” said a health ministry spokesman, Dr Kanishka Turistani, in the early afternoon.

A Taliban-linked group, led by the former Mujahideen warlord Gulbuddin Hekmatyar, claimed responsibility for the attack. A spokesman for Hizb-e-Islami, Haroon Zarghoon, said the group had attacked “American advisers” working in the city.

Additional reporting by Mokhtar Amiri.

Guardian Service