Nato tankers torched in Pakistan
Suspected militants in southern Pakistan have destroyed at least 27 tankers carrying fuel for Nato forces in Afghanistan, officials said.
There have been many similar ambushes in Pakistan in recent years, but this is the first one in this part of the southern province of Sindh.
It is not clear if it is linked to a cross-border air strike by Nato that killed three Pakistani troops.
Pakistan has blocked supply routes to Afghanistan after Thursday's air raid.
No-one has claimed responsibility for Friday morning's raid in the town of Shikarpur, which is in the north of Sindh province.
The town's district police chief, Abdul Hameed Khosa, told the BBC the oil tankers - which picked up their load from the southern port of Karachi - were parked in a petrol station at the time of the attack.
Up to 15 gunmen armed with rocket launchers and assault rifles opened fire to scare away the drivers, before setting the vehicles ablaze, said witnesses.
Attacks on Nato supply convoys are rare in southern and central Pakistan, so security forces do not provide the escort that is routine in the north-west of the country.
While these tankers have been targeted several times in the city of Karachi, the capital of Sindh, such incidents have never occurred elsewhere in the province.
"This is the first major attack on Nato trucks in Sindh," Sindh provincial government spokesman Jamil Soomro told the news agency AFP.
The ambushes have mainly happened in the north-western Khyber tribal region or in the south-western province of Balochistan.
The BBC's Aleem Maqbool in the Pakistani capital says the latest attack will certainly be seen as a reaction to Thursday's killing of three Pakistani border guards in a missile strike by Nato helicopters.
Nato said its aircraft had hit back after coming under small-arms fire from what it thought were insurgents.
But the Pakistani military said its soldiers had fired shots to warn the helicopters that they had crossed into Pakistani airspace.
Islamabad has instructed its ambassador to Brussels to lodge a strong protest at Nato headquarters over the missile strike.
It was the third time in less than a week that Nato helicopters had pursued militants over the Pakistani border and fired on targets.
Numerous protests over the deaths are expected across Pakistan later to coincide with Friday prayers.
A long queue of Nato vehicles is now waiting to drive over the border at the shut Torkham border crossing in Khyber tribal agency.
The other main Nato crossing from Pakistan to Afghanistan - Chaman in Balochistan - remains open.
It is not clear whether the tanker convoy attacked on Friday was heading for Torkham or Chaman.
Nato says the border closure has had "no impact" on the supply of goods and transport logistics so far. It says the trucks passing through Pakistan carry fuel, military vehicles, spare parts, clothing and other non-lethal supplies for foreign troops in Afghanistan.
The alliance and the US have other supply routes into Afghanistan, but the Pakistani ones are the cheapest and most convenient.