The FC personnel had arrested two suspects from the Pak-Afghan border the previous night and were taking them to the headquarters for interrogation when the blast occurred.
The explosives were reportedly inside the belongings of the suspects.
Both FC personnel were killed on the spot while their vehicle was destroyed.
There was no information on the suspects being killed or injured.
Violence has surged in the province this year and human rights activists have raised concerns about an increase in targeted killings.
The FC have been a target of many attacks this year, most frequently on Saryab Road in Quetta.
Earlier, a bicycle bomb apparently targeting security forces killed two people and injured nine others, including Frontier Corps (FC) personnel with 5kg explosives.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ