Initial reports spoke of a terrorist bombing, but police later said gunpowder stored in an ammunition shop caused the explosion. The event shook the jittery Afghan capital, which has been expecting more Taliban-inspired suicide bombings.
The massive explosion destroyed part of Kabul's old city center, sending a towering column of dust into the air and shattering windows up to 1 kilometer away.
"Two of my nephews were [killed] in this explosion," a witness, Haji Qudbuddin told Reuters. "We don't know what caused it, but it was a very loud and terrible explosion."
"Our investigation continues," Afghan police official Samanwal Abdulrahman said. "According to the latest figures six people have been [killed] and nine have been injured."
Death Toll Likely To Rise
The police said they expect the toll to rise as rescue workers dig through the rubble of dozens of mud-brick shops destroyed in the blast. Most of the casualties came when people were trapped under falling debris.
Kabul suffered a number of suicide bombings last year that killed dozens of people, and the Taliban insurgency has promised to follow up such attacks with fresh bombings this year.
Initial reports of today's incident said there had been a bomb attack on a police patrol in the city.
But General Ali Shah Paktiawal, the criminal director of the Kabul police, later dismissed such a possibility in remarks to RFE/RL's Radio Free Afghanistan.
"It was an incident that happened unintentionally," Paktiawal said. "It was not a suicide attack or an explosion by the enemies of the government."
The police said they believed gunpowder and dynamite had accidentally detonated in a shop selling hunting guns and supplies.
"Two of my nephews were [killed] in this explosion," a witness, Haji Qudbuddin, told Reuters. "We don't know what caused it, but it was a very loud and terrible explosion. God knows better what the cause was."
AFP reported that the blast left a 3 meter crater in the ground. Broken shotguns, air guns, and bullets were scattered in the debris of bricks, wood, blankets, water pipes, and cables.
The shop owner is believed among those who were killed.
It's not clear why large quantities of gunpowder and dynamite were being stored in the shop, but a police colonel who did not wish to be identified said it appeared that the materiel may have been used for illegal mining operations.