The explosion, triggered by an improvised explosive device, took place in Spinkai area of South Waziristan, administration officials said.
Peoples' Aman Committee Commander Wali Jan and the school teacher was among the five persons killed, they said.
It was the third attack on Jan, they added.
The committee was said to be part of a volunteers' militia helping the military in operations against Islamist militants, officials said.
No group has claimed responsibility for the attack but Taliban militants often target security forces in the area.