The attack took place near the town of Wadh in Khuzdar district, 360 kilometres south of Quetta, local police official Jumma Khan told AFP.
Unknown gunmen flagged the vehicle to stop and opened fire when the driver ignored them, Khan said, adding that the driver was killed and his helper was wounded. The attackers set the vehicle on fire, he said.
Nato supply trucks and oil tankers are targets of frequent attacks blamed on insurgents attempting to disrupt supplies for international troops fighting in Afghanistan.
Most supplies and equipment required by coalition troops in Afghanistan are shipped through neighbouring Pakistan, although US troops increasingly use alternative routes through central Asia.
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