Pakistan has begun building a fence on its disputed 2,500 km (1,500 mile) border with Afghanistan to prevent incursions by militants, Pakistan's army chief said, in a move likely to further strain relations between the two countries.

Pakistan has blamed Pakistani Taliban militants it says are based on Afghan soil for a spate of attacks at home in recent months, urging Kabul to eradicate "sanctuaries" for militants.

Citing the attacks, Islamabad earlier this month temporarily shut the main crossing points along the colonial-era Durand Line border, drawn up in 1893 and rejected by Afghanistan.

General Qamar Javed Bajwa said 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.

Pakistan has long harboured ambitions to seal its border, which is largely unpatrolled and mountainous for large chunks.

In 2007, the military said it was fencing and mining a 35 km (22 miles) stretch of border in the North Waziristan region of FATA to prevent militants crisscrossing the rugged terrain.

Efforts to establish a more permanent presence on the disputed frontier have angered Kabul. Last year, Pakistan's attempt to build a barrier on the main Torkham crossing ended in brief cross-border skirmishes.

In recent weeks at least two U.S. drone strikes have targeted Pakistani militants on the Afghan side of the frontier.