Image caption The latest clashes have stoked nationalist sentiment among many Afghans

Afghan and Pakistani troops have clashed across the border between the two countries for the second time in a week.

There are no reports of serious casualties in the latest clashes.

One Afghan border police guard was killed and two Pakistani troops injured in violence on Wednesday.

The renewed fighting comes after Afghan President Hamid Karzai said his government would never recognise the current border with Pakistan.

Afghan grievances over the frontier with Pakistan date back to its being drawn as the so-called Durand Line by the then colonial power Britain in 1893, the BBC's David Loyn reports from Kabul.

The governor of the Afghan province of Nangarhar said that several Pakistani border checkpoints were torn down just south of the Khyber Pass.

The Afghan foreign ministry summoned the Pakistani charge d'affaires Shah Nazar Afridi in Kabul to lodge a "strong protest" over the latest violence, according to a statement.

The ministry said that Mr Afridi was told that Pakistan would "bear responsibility for any consequences" if it refused to move Pakistani posts in areas which Afghanistan says are inside its territory.

Pakistani officials say Afghan forces initiated the latest violence.

Thousands of Afghans took part in anti-Pakistan protests in the Afghan capital Kabul on Monday.

The border police officer killed in the previous clash has been hailed as a martyr amid rising nationalist fervour on social media sites in Afghanistan, our correspondent reports.

Afghanistan believes that Pakistan is taking advantage of the reduction in US forces, seizing ground and setting up new border posts, he adds.

There has been no official Pakistani comment on the latest clashes, but a Pakistani foreign ministry spokesman insisted that the Durand Line was the settled frontier, and that Pakistani checkpoints were vital for good border management.