Angered by repeated incursions by Nato helicopters over the past week, Pakistan has blocked a supply route for coalition troops in Afghanistan.
Pakistan is a crucial ally for the US in its efforts to stabilise Afghanistan, but analysts say border incursions and disruptions in Nato supplies underline growing tensions in the relationship.
A senior Pakistani intelligence official said the border incursions could lead to a “total snapping of relations”.
Senior local officials blamed “extremists” for the attack on the tankers in the southern town of Shikarpur. About 12 people, their faces covered, opened fire with small arms into the air to scare away the drivers and then set fire to 27 tankers.
“Some of them have been completely destroyed and others partially. But there is no loss of human life,” Shikarpur police chief Abdul Hameed Khoso said.
Police arrested 10 people after the attack, including five netted from a raid on an Islamic seminary, or madrassa.
The tankers were parked at a filling station on their way to Afghanistan from Pakistan’s southern port city of Karachi.
On Thursday, three Pakistani soldiers were killed and three wounded in two cross-border incursions by Nato forces chasing militants in Pakistan’s northwestern Kurram region.
It was the third cross-border incident in a week, the Pakistan military said.
The Nato said the helicopters briefly crossed into Pakistan airspace after coming under fire from people there.
Prime Minister Yusuf Raza Gilani, speaking in Parliament, said Pakistan was a partner in the war against Islamist militancy, but would allow no infringement of its sovereignty.
“I want to assure the entire nation from this house that we will consider other options if there is interference in the sovereignty of our country,” Gilani said without elaborating.
Pakistan’s ambassador to Belgium lodged a protest with Nato’s deputy general secretary over the incursions, the Pakistan embassy said in a statement received in Islamabad.