At least one woman was killed and eight other people were wounded, the interior ministry said, citing preliminary information.
"There has been an explosion against a minibus in Kabul," Kabul police spokesman Basir Mujahid told AFP, adding that more casualties were feared. "Police are investigating the nature of the explosion."
Gunmen disguised as doctors stormed Afghanistan's largest military hospital last Wednesday, killing more than 100 people in a brazen six-hour attack, multiple surviving staff and security sources told AFP.
Insiders including two interns already positioned inside the facility were among the attackers, the sources said.
The carnage inside the heavily guarded hospital points at a spectacular intelligence failure and spotlights how insurgents have managed to infiltrate top government and military institutions in Afghanistan.
The savagery of the assault was characterised by how the assailants stabbed bed-ridden patients, threw grenades into crowded wards and shot people from pointblank range.
The ISIS terror group claimed it was behind the attack via its propaganda agency Amaq - hours after the Taliban denied responsibility.
But the survivors AFP spoke to said the attackers chanted "Allahu Akbar" (God is great) and "Long live Taliban" in Pashto.