The attack, the latest in a series to hit the Afghan capital over the past several days, came with the city under tight security ahead of this week's Eid al-Fitr holiday ending the Muslim holy month of Ramadan.

Interior Ministry spokesman Nasrat Rahimi said the bus was carrying employees of the Independent Administrative Reform and Civil Service Commission.

No one immediately claimed responsibility for the attack, which came only hours after the Interior Ministry briefed media on security measures in large cities ahead of Eid.

Both Taliban and Islamic State militants have staged attacks in Kabul, which was hit by a wave of attacks over the past week.

Four bombings on June 2 killed at least two people and wounded 27. They came after deadly suicide bombings on May 30 and May 31.

Based on reporting by AP, AFP, and Reuters