The victims had gathered around the tanker to collect oil leaking from it after the bomb attack Friday night.
The tanker was parked in the Khyber tribal region's Torkham parking hub and was bound for Afghanistan.
Security forces have cordoned off the area.
Pakistan is the main supply route for NATO-led forces battling Taliban militants in landlocked Afghanistan.
Militants frequently attack oil tankers and trucks bringing goods from the Pakistani port of Karachi to Afghanistan.
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