Further details were not immediately available.
The Afghan capital is heavily fortified but has still been attacked multiple times this year by insurgents.
In one of the worst incidents in February, insurgents used a car bomb and militants in suicide vests to kill at least 16 people -- half of them foreigners -- in the heart of Kabul.
The Afghan government has since stepped up police checkpoints to create what it calls a "ring of steel" around the capital.
Rockets hit a national peace conference in June, and security officials have said they thwarted planned suicide attacks in Kabul during a recent international conference on the future of Afghanistan.
