There was no immediate claim of responsibility for the explosion, which shook the center of the capital and ripped through homes and shops. A Taliban spokesman said it was looking into the incident, while government officials said an investigation was under way.
“A truck bomb detonated close to an army compound,” said Kabul police chief Abdul Rahman Rahimi, adding that at least eight bodies had been found.
The health ministry said around 400 people, many wounded by debris and flying glass shattering in buildings damaged by the blast, had been taken to hospital.
The explosion, in a heavily populated area, left hole in the ground more than 10 meters deep, reduced nearby buildings to rubble and damaged cars at least a hundred meters away, a Reuters witness said.
Police expect the number of dead to rise, as buildings had collapsed and bodies were feared buried in the wreckage.
The blast was unusually powerful in a city that is frequently targeted by the Taliban and other militants seeking to destabilize the Afghan government.
Smaller magnet bombs or suicide attacks have become a weekly occurrence in the heavily fortified capital, but large truck bombs have rarely penetrated the city’s outskirts.
A Western security source said the target was probably a compound used by Afghan intelligence officials and that as many as 15 people had been killed.
An official at the Emergency Hospital in Kabul said the facility had been flooded with almost a hundred patients, including many women and children.
The Afghan war between the foreign-backed government and the Taliban has intensified since the NATO combat mission ended last year and most foreign troops were withdrawn.
Afghan security forces are battling the Taliban with only limited support from coalition forces this year and have sustained heavy losses.
Around 4,000 army and police are lost each month to casualties and desertions, the U.S. general in command said this week.
Dozens of clashes are reported every day and civilians are frequently caught in the crossfire. The truck bomb was the second huge explosion to target security forces in 24 hours.
On Thursday, a truck bomb targeting an Afghan special forces base exploded in eastern Logar province, killing at least three soldiers and wounding dozens.