Nobody has claimed responsibility for Tuesday's bomb attack on a NATO tanker waiting at the Torkham border post, which Pakistan sealed six days ago.
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The attack underscored the heightened threat posed to NATO supply lines amid Pakistan's closure of the border post six days ago to protest the death of three of its soldiers in a NATO helicopter strike. A backlog of NATO tankers and trucks cannot pass through Torkham.
Tuesday's attack on a NATO convoy was the fifth such attack since the border closure began, reports the BBC. No one has claimed responsibility for the blast yet, although the Pakistani Taliban have admitted to previous convoy attacks, including one Monday that killed at least three people and destroyed nearly 30 vehicles.
Wajid Khan, a local official in the Khyber tribal region, where Torkham is located, told the Associated Press that an explosive device was planted underneath the truck while it waited with more than 100 others to cross into Afghanistan. Oil began leaking out of the truck after the explosion, but no injuries or fire were reported.
A spokesman for the Pakistani Taliban, Azzam Tariq, told CNN that the group accepts responsibility for two of those attacks, which resulted in six deaths. He said the attacks were retaliation for US drone strikes in Pakistan and had been carried out by a "special squad" tasked with striking US targets in the country.
"US and NATO forces are killing innocent Pakistanis, which is unacceptable, and we will teach them a lesson by such attacks," Tariq told CNN. "The special squad is fully capable to cut off the route for NATO supplies by carrying attacks on the trucks."
But it is Pakistan's government, and not the Taliban, that has cut off NATO's supply route, bowing to public anger over US drone attacks and air strikes by manned aircraft on Pakistani targets. September saw 21 drone strikes in Pakistan, a record number, with three more strikes occurring so far in October, reports Reuters.
Hundreds of supply trucks have been stuck on the Pakistan side of the border since the closure began. Pakistani daily newspaper Dawn reports that by Sunday, four days after the crossing was shut, as many as 200 oil tankers and other supply trucks were sitting in Torkham crossing because they had been "rejected clearance to proceed." An unknown number of other supply trucks had been barred from approaching the border post and diverted back to the city of Peshawar.
Dawn reports that Pakistan's Foreign Ministry has said the border crossing will be reopened "after public anger over the NATO strikes eases."
NATO officials have taken steps to ease that anger. On Monday, NATO Secretary-General Anders Fogh Rasmussen apologized for the death of the Pakistani troops after a meeting with Pakistan's Foreign Minister, Shah Mehmood Qureshi, and urged the coalition and Pakistan to continue working together.
"I expressed my regret for the incident last week in which Pakistani soldiers lost their lives," Reuters quotes him saying, "I expressed my hope the border will be open for supplies as soon as possible… It is important we step up our cooperation."
Torkham is one of the main supply routes for international forces in Afghanistan, but CNN reports that it is far from the only one. Half the supplies entering the war zone come through Pakistan via two border posts, one in southern Afghanistan and one in the east. The other half does not transit through Pakistan at all. Thirty percent of NATO supplies enter from the north, through Kazakhstan, Uzbekistan, Russia and the Caucasus, while the other 20 percent, including sensitive materials such as weapons and ammunition, arrives by air.
(For a BBC map of NATO supply routes in Pakistan, see the bottom of this page.)