Officials said up to 25 lorries were set on fire but there were no injuries or deaths [AFP]
Tankers carrying supplies for Nato troops in Afghanistan have been set on fire by unidentified assailants in the Pakistani town of Shikarpur in Sindh province, officials say.
The incident on Friday came a day after Pakistani authorities blocked a supply route for Nato troops, angered by the killing of three Pakistani soldiers in airstrikes by Nato helicopters.
"The attackers fired with small arms on tankers and fled away. No one was hurt," an official of the paramilitary Rangers force told the Reuters news agency.
The official, who declined to be named, said about 10 assailants attacked up to 25 to 30 tankers early in the morning.
Efforts were underway to put out the fire, a police official, Mir Hazar Chandio, said.
The supply route remained blocked on Friday and lorries were not allowed to enter Afghanistan for the second consecutive day, an administrative official said.
"Trucks carrying fuel and other goods for Nato are still not allowed to enter Afghanistan," the official, speaking from Torkham, the main crossing border between Pakistan and Afghanistan, told the AFP news agency by telephone.
The three Pakistani soldiers were killed on Thursday in two cross-border strikes as Nato troops were chasing anti-government fighters in Pakistan's northwestern Kurram region.
Hours later, Pakistani authorities halted tankers carrying supplies for the Nato forces passing through the Khyber tribal region on the Afghan border.
Al Jazeera's Kamal Hyder, reporting from the the Pakistani capital, Islamabad, said the blocked route is a "very crucial part of the supply chain because most of the aviation fuel [for Nato aircraft] goes through Pakistan".
"It's that aviation fuel that's used in combat missions inside Afghanistan," he said.
Our correspondent said previous attacks on Nato convoys have taken place in Balochestan or the province of the North-West Frontier and that Friday's attack in the southern province of Sindh was a rare occurence.
Pakistan is a key ally for the United States in its efforts to stabilise Afghanistan, but analysts say border incursions and disruptions in Nato supplies underline growing tensions in the relationship.
The bulk of supplies for the troops in Afghanistan goes through Pakistan.
Source: Al Jazeera and agencies