At least seven tankers carrying fuel for Nato troops in Afghanistan were gutted on Monday when a bomb planted in one of the vehicles exploded at a terminal in Pakistan, officials said.
"A bomb fitted with a timer blew up an oil tanker. It triggered fire that engulfed six more tankers," local administration official Shahar Yar Khan said. There were no reports of any casualties, he added.
Another official in the area said more than 30 fuel tankers were parked at a terminal in the Torkham border area of the troubled Khyber tribal region.
Most of them had been moved away but the raging blaze was threatening another 10 tankers still in the area, he said.
No group has claimed responsibility for the blast but the Taliban has in the past said it carried out such attacks to disrupt supplies for more than 130,000 US-led international troops fighting in Afghanistan.
Taliban and al Qaeda-linked militants frequently launch attacks across northwestern Pakistan and the lawless tribal belt on the Afghan border, which Washington has branded the most dangerous place in the world.
Most supplies and equipment required by the soldiers in Afghanistan are shipped through Pakistan, although US troops increasingly use alternative routes through Central Asia.