Afghan officials say a sticky bomb attached to a police vehicle went off near a campaign rally by President Ashraf Ghani in the country's northern Parwan province.
There was no immediate word of casualties in the explosion.
The president's campaign spokesman Hamed Aziz says that Mr Ghani was there but that he is safe and unharmed. Mr Aziz said he would provide more details later.
Wahida Shahkar, spokeswoman for the provincial governor in Parwan, says the explosion happened while the rally was underway on Tuesday, at the entrance to the venue.
No group immediately claimed responsibility for the attack.
Across Afghanistan, militant attacks have continued as the country
