Islamabad, Pakistan (CNN) -- Another oil tanker carrying fuel for NATO troops in Afghanistan was attacked Tuesday near the Pakistan-Afghanistan border, a Khyber Agency official told CNN.
The tanker had been parked at Torkham, said Adil Waseem, senior administration official of Khyber Agency. A bomb planted on the tanker exploded, partially damaging the vehicle. The tanker did not catch fire, and no casualties were reported.
At least four other attacks have been carried out on convoys for NATO since Friday, resulting in the deaths of at least six people.
The Pakistani Taliban has claimed responsibility for two of those attacks, a central spokesman for the militant group told CNN by telephone Monday.
"U.S. and NATO forces are killing innocent Pakistanis, which is unacceptable, and we will teach them a lesson by such attacks," Tariq said.
Islamabad police said four people have been arrested in connection with the Sunday attack, which also left eight drivers injured.
The Pakistani Taliban said a special squad has been appointed to hit U.S. interests in Pakistan, especially NATO supply efforts.
"The special squad is fully capable to cut off the route for NATO supplies by carrying attacks on the trucks," Tariq said.
Supply convoys are all-important for the Afghan war effort. Coalition forces rely heavily on convoys from Pakistan to bring in supplies and gear. They are generally operated by contracting Pakistani logistics firms, using local trucks and drivers.
Torkham Gate is one of the main ports of entry for material coming into the war zone. But it is not the only way of getting supplies in. Khyber Agency is one of the seven districts in Pakistan's tribal region.
About half the cargo that flows into Afghanistan comes in via one of the two gates from Pakistan, the U.S. Defense Department says.
Another 30 percent uses two major routes through Kazakhstan and Uzbekistan, one via Russia and the other via the Caucasus. The remaining 20 percent -- mostly sensitive items like weapons, ammunition and other critical equipment -- comes in by air.