KARACHI: Pakistani transporters who carry Nato supplies to land-locked Afghanistan have gone on strike, disrupting the flow of goods to Western forces in a protest against a new customs regime aimed at cutting theft.

A spokesman for Afghanistan’s Nato-led force declined to comment on how the strike might affect supplies. When Pakistan previously blocked supplies it cost $100 million extra a month to send supplies on longer, alternate routes, US officials said at the time.

The All Pakistan Goods Transportation Association has been unofficially blockading 4,000 vehicles carrying supplies to and from coalition forces in Afghanistan for the past six days.

The truckers are protesting against a new government-imposed system that will require them to go through authorised companies to carry Nato supplies instead of making individual deals. The system is designed to cut down on theft.

Transporters say that will hurt their business and they have announced that operations would remain suspended until the system is scrapped.

“We will continue striking as long as our demands aren’t met,” transporter Abdul Ghafaaz Niazi said on Wednesday.

“Custom collectorate officials are corrupt. We won’t listen to them. If they want to lose billions of rupees every day, they can.”

Syed Shams Ahmed Burney, chairman of the All Pakistan Custom Bonded Carriers Association, said the transporters’ demands were impractical.

“This system exists to minimise and end pilferage and theft but the transporters want a free-for-all. That is not possible,” he said.

Many supplies for US and other forces in Afghanistan are shipped into the Pakistani port of Karachi and trucked along two routes into Afghanistan.

Pakistan previously banned trucks from carrying Nato-force supplies into Afghanistan in 2011 in protest against a cross-border Nato air strike that inadvertently killed 24 Pakistani soldiers.

The seven-month ban forced the United States to rely on longer, more expensive northern routes through Russia and Central Asia.

The blockade was lifted after US Secretary of State Hillary Clinton apologised for the losses suffered by the Pakistani military in the Nato attack.