At least 42 people were injured in the blast and there are fears the number of casualties could rise.
The blast in the west of the city, in a mainly Shia district, struck a bus carrying government employees from the ministry of mines, officials said.
The Taliban said they had carried out the attack and were targeting intelligence service officials.
Kabul has seen a number of deadly attacks this year blamed on the Taliban or so-called Islamic State.
Security forces cordoned off the area of Monday’s blast, which took place during the rush hour.
Three vehicles and 15 shops were damaged or destroyed.
The district where the blast occurred is home to many of the minority Shia Hazara community.
The blast was close to the home of deputy government Chief Executive Mohammad Mohaqiq, a leader of the Hazara community.
There have been several recent attacks in the district, including one that killed senior Shia cleric Ramazan Hussainzada last month.
A Taliban spokesman claimed the bus had been under surveillance for months and was carrying “intelligence workers”.
According to the United Nations, the country has seen at least 1,662 civilian deaths in the first half of the year with around 20% of those in the capital.