Trucks carrying supplies for NATO troops in Afghanistan crossed the Pakistani border on Thursday for only the second time since Islamabad agreed to lift a seven-month blockade, officials said.
Pakistan closed overland routes for NATO convoys going to its war-torn neighbour after botched US air strikes killed 24 Pakistani soldiers in November, plunging ties between the "war on terror" allies to a new low.
Islamabad agreed to reopen the routes after US Secretary of State Hillary Clinton said sorry for the deaths on July 3.
But traffic has been sluggish.
Until Thursday, only a few trucks had been cleared to enter Afghanistan, with thousands of drivers awaiting compensation before going back to work, and saying the trips into Afghanistan are too dangerous and too poorly paid.
The Pakistani Taliban has threatened to attack NATO supply trucks and kill drivers if they resumed trips to Afghanistan.
On Thursday, the umbrella militant organisation threatened a further wave of attacks, and claimed responsibility for shooting nine police prison officers being trained in the eastern city of Lahore.
"Four NATO trucks carrying food supplies crossed the border," Pakistan customs official Hassan Agha told AFP.
Customs official Maqsood Ahmed confirmed three NATO containers were allowed to cross the Chaman border post in Pakistan's remote southwest after clearing customs on Thursday.
Deputy commissioner of Chaman, Bashir Khan Bangalzai, said the trucks were provided security by tribal police and paramilitary forces.
In the northwestern tribal district of Khyber, officials said seven to 10 trucks loaded with NATO supplies were due to cross the Torkham post for the first time since Pakistan agreed to resume supplies.
"All of them will cross the border today," customs official Ubaid Ullah told AFP.
But in Karachi, where NATO containers are loaded onto trucks after being shipped to the port, many are still waiting for compensation from NATO subcontractors for being out of work for seven months.
"We are too wary, too anxious and too cautious about the situation. It was dangerous to go overland before the government ban, but now the dangers have increased," Akram Khan Durrani, president of the All Pakistan Oil Tankers Owners Association, told AFP.
"No one from the authorities have contacted us properly and assured us of fool-proof security," he said.