Hashmat Stanekzai, the spokesman for Kabul's police chief, says a roadside bomb targeted an Afghan National Army minibus early today morning, causing the casualties.
The Kabul provincial police chief, Gen Mohammad Zahir, says the second blast in the center of the city a few hours later did not cause any casualties.
Kabul has seen an escalation in attacks by insurgents in recent months, many targeting foreigners and security installations.