"The peace committee members could not even retaliate," media reports here quoted an official of the political administration as saying.
The militants have also kidnapped four members of the committee.
Two of the beheaded bodies were found after the incident in Qamabarabad Shalobar. The reports, however, did not give details about the third body.
"The militants threw two of the heads on the way and warned the locals not to pick them before 12 noon on Monday," an official was quoted as saying by The Express Tribune.
He said those killed had freshly joined the committee as volunteers.
The four kidnapped members could not be identified.
The bodies were shifted to the levies forces centre at Shahkas and later handed over to their families.
As part of counter-terrorism strategy, the government had encouraged local tribesmen to set up militias to fight against the Taliban and other militant groups.