Those killed in the attack outside Camp Chapman included a security guard and two delivery truck drivers, CNN reported, quoting provincial police chief Abdul Qayoom Baqizoy. Those injured were civilians.
The blast occurred a minibus was stopped at the gate of the base for security check at the city near the Pakistani border.
The Taliban claimed responsibility for the attack, CNN said.
NATO's International Security Assistance Force said the base had been secured.
Camp Chapman is where seven CIA operatives and a Jordanian intelligence official died in a suicide bombing Dec. 30, 2009.