Two oil tankers carrying fuel for US forces in Afghanistan exploded in Chaman near the Afghan border, officials said on Thursday.
"It appears to be an act of terrorism," Chaman administration official Nazar Hussain told AFP, adding the cause of the blast was being investigated.
The Shell company tankers were at a petrol station near Chaman, which borders Afghanistan's insurgency hit Kandahar province, when they exploded shortly after midnight on Wednesday, they said.
The tankers were loaded at Karachi, from where oil is routinely shipped to Kandahar for US-led coalition forces in Afghanistan.
Last month, three people were injured when an oil tanker bound for southern Afghanistan exploded and gutted three trucks at a check-post in Chaman.
Taleban fugitives, who are believed to be active in the region around Chaman, claimed responsibility for that blast, residents said.