Ahmed was on his way to a rally at Halimzai area of Mohmand Agency when the bomb was detonated by remote control, officials of the local political administration told the media.
One of the vehicles in Ahmed's motorcade was hit by the blast and three of his supporters were injured, they said.
The former Jamaat-e-Islami chief escaped unhurt and later participated in the rally.
The bomb attack occurred less than a kilometre from the venue of the rally.
No group claimed responsibility for the attack.
