Nato supply trucks are regularly attacked in Pakistan
Suspected militants have blown up more than 20 vehicles carrying Nato supplies from Pakistan's Karachi port to Kandahar in Afghanistan, police said.
Two people have been injured in the attack, they said. No one has claimed responsibility for the attack.
The attack occurred when the border was closed to traffic after a dispute between Pakistani and Afghan officials.
The Taliban regularly carry out attacks on trucks ferrying supplies for Nato in Afghanistan.
In the latest incident late on Sunday, militants detonated remote-controlled explosives to destroy more than 20 oil tankers and trailers.
Police and witnesses said there was a huge explosion, presumably under one parked oil tanker.
The tanker burst into flames and the fire soon engulfed other oil tankers nearby.
The border was closed on Saturday when Afghan truckers carrying fruits and other supplies into Pakistan accused Pakistani border guards of forcing them to offload their goods at the crossing for security checks.
They said the exercise was time consuming, and damaged the perishable fruits they were carrying.
On Sunday, at a press conference at Spin Boldak, the Afghan town near Chaman, Afghan truckers accused the Pakistani paramilitary Frontier Corps personnel of demanding bribes.
They said those truckers who paid the officials 500 rupees were not asked to offload their goods.
A spokesman of the Frontier Corps in Quetta, Murtaza Beg, refuted this claim.
"We have strict orders to check all trucks and containers coming in from Afghanistan since April this year when more than 40 Afghan nationals suffocated to death in a container in a human smuggling racket," he told BBC Pashto Service's Ayub Tarin.
Mr Beg denied that the truckers were being asked to offload their goods.
But a Pakistani customs official at Chaman border, Shahid Abbasi, told the BBC that the Afghan truckers blocked cross-border traffic when they were asked by the security forces to offload their goods.
"It is a dispute between the security forces and the Afghan government officials, and does not involve Pakistani customs officials who have no role in checking vehicles at this border crossing," he said.