At least 15 people have been killed and dozens wounded in a suicide bomb attack on a military convoy in the Afghan capital, Kabul, officials say.
Two US soldiers and four civilian contractors were among the dead, US and Nato officials said.
Nine Afghan civilians, including two children, were also reported to have died in the blast.
An Islamic militant group, Hezb-e-Islami, told the BBC in a phone call it was responsible.
The explosives-filled Toyota Corolla was blown up beside foreign military vehicles at about 08:00 (03:30 GMT), Kabul Police Chief Gen Salangi said.
Nato confirmed that four civilian contractors had been killed, but declined to give their nationalities.
The US military said two of its soldiers had been killed.
Smoke rose above the industrial district of Karta-e Naw after the powerful explosion.
The force of the blast destroyed several houses and a wide area of the city has been cordoned off. At least 35 people were injured.
Afghan President Hamid Karzai condemned the "cowardly" attack.
"Terrorists and enemies of Afghanistan's peace brutally targeted a residential area," he said in a statement.
A local resident told AFP news agency: "I heard a terrible explosion and our whole building shook."
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.
Hezb-e-Islami is based in north-eastern Afghanistan and is led by the former prime minister Gulbuddin Hekmatyar.
The group claims to have formed a new cell to carry out suicide attacks on coalition forces, according to the Associated Press news agency. While not part of the Taliban, the insurgent group shares many of its aims.
Most international troops are scheduled to leave Afghanistan by the end of 2014, and Afghan forces are due to take responsibility for the security of the whole country in the next few months, for the first time since 1992.
Reproduced under licence from BBC News © 2013 BBC