Afghan officials have said a suicide bomber, who killed six outside NATO headquarters in Kabul, four of them children, could have been as young as 12.
The boy is said to have posed as a street urchin, who sell small gifts to foreigners in the capital. But his rucksack was full of explosives.
A member of the Afghan security forces stands guard at the scene of a suicide bombing in Kabul Afghanistan
Haji Wasiullah Taj, chief of the district where the bombing occurred, said the boy was between 12 and 14. "A lot of sellers go down this road and the security teams thought he was one of them, but he was not known to the children here.
"His aim was to get to Nato headquarters or the US embassy. The other children were apparently giving him a hard time, but we don't know the reason why he detonated here."
Most of his victims were the same age, street children gathered around the NATO buildings. The Guardian named two of the four killed as sisters Khorshid, 13, and Fatana, aged eight.
Hashmat Stanikzai, a police spokesperson, said the dead and wounded were all street sellers aged between 12 and 17. The area is home to many diplomat buildings, including Western embassies.
The Taliban, which claimed responsibility for the attack, said the bomber was not a teenager, claiming he was 28.
The attack came just days after Prince Harry arrived in the country to begin his four-month deployment.
Taliban spokesman Zabihullah Mujahid said the target was a CIA base, and said it was a lie that only children were killed.
He said the bomb had killed US soldiers, despite eyewitnesses reporting all of the six dead were Afghan. "One of our mujahideen targeted an important intelligence office used for recruiting Americans and Afghans for spying," he said.
The Afghan Ministry of Interior said the attack could have been orchestrated by the Taliban-linked Haqqani network, as a retaliation for being officially declared a terrorist group by the US on Friday.
No NATO or international military forces were injured or killed in the attack.
Afghans carry a wreath of flowers during a ceremony commemorating the11th anniversary of the death of Ahmad Shah Massoud
Security in the capital had been beefed up as the bombing coincided with the 11th anniversary of the death of anti-Taliban campaigner Ahmad Shah Massoud.
The Northern Alliance commander was killed in an al-Qaeda suicide bombing two days before the 9/11 attacks in 2001.
Hamid, a 23-year-old man told al-Jazeera he was searching for his 15-year-old brother: "These are all animals, the Taliban who kill our people everyday. They told me my brother was brought to this hospital. I'm trying to get in to see him.
The attack was the deadliest in the capital since June, when Taliban militants killed 18 people at a hotel.