Pakistan has started building a fence along the disputed 2,500km Durand Line in areas Islamabad deems “high threat zones”.

Islamabad has long blamed alleged insurgents based in Afghanistan for attacks on Pakistan soil.

This comes after Islamabad closed the main crossings between Afghanistan and Pakistan for a month – only reopening gates last week – a move that cost traders millions of dollars.

Reuters quoted Pakistan’s Army Chief of Staff General Qamar Javed Bajwa as saying initial fencing will focus on "high threat zones" of Bajaur and Mohmand agencies in the Federally Administered Tribal Areas (FATA), which border eastern Afghan provinces of Nangarhar and Kunar.

"Additional technical surveillance means are also being deployed along the border besides regular air surveillance," the military said in a statement over the weekend, citing Bajwa.

There was no immediate comment from Afghan authorities.

Relations between Kabul and Islamabad have been tense in recent years, with both countries accusing each other of not doing enough to tackle Pakistani and Afghan Taliban militants.

Afghanistan has accused Pakistan of turning a blind eye to Afghan Taliban commanders on its soil and even of supporting the militant group, something Islamabad denies.

Bajwa said Pakistan was working on plans to "evolve a bilateral security mechanism" with Afghanistan.

"A better managed, secure and peaceful border is in mutual interest of both brotherly countries who have given phenomenal sacrifices in war against terrorism," Bajwa added.

According to media reports and the Wall Street Journal, Najib Danish, the deputy spokesman for the Afghan Interior Ministry, said officials had not yet seen any signs of construction along the frontier but would move to prevent any such project.

“Building fences or any construction is not acceptable for us and we won't allow anyone to do it," he was quoted as saying.