A suicide bomber on a motorcycle detonated explosives close to Sunday's procession commemorating the death of former anti-Soviet mujahideen commander Ahmad Shah Massoud, a police spokesman said.
The blast, which wounded at least two people, came hours after another suspected suicide bomber was shot by police in Kabul before he could detonate his device.
Earlier, gunfire could be heard across the city as demonstrators fired automatic weapons in aggressive displays of support for Massoud, an ethnic Tajik leader who was killed by suicide bombers in 2001.
With parliamentary elections approaching next month and rivalry between Afghanistan's ethnic groups on the increase, the annual commemoration day for Massoud has created a tense atmosphere in Kabul, where major roads were blocked by police.
The blast came four days after more than 20 people were killed by a suicide bomber at a wrestling club in Kabul as well as a secondary blast apparently aimed at first responders and journalists.