Pakistani and Afghan officials accused each other of killing civilians Friday after gunfire erupted near a major border crossing where Pakistani census officials were carrying out a count.
The gunfight prompted Pakistani authorities to shut the Chaman border crossing, one of only two major crossing points along the disputed frontier, and threatens to exacerbate already tense relations between Islamabad and Kabul.
"Afghan border police opened fire on FC (Frontier Corps) detailed for security of population census team," the Pakistani military said in a statement, adding that one civilian had been killed and 18 others, including four soldiers, injured.
It accused Afghan officials of "creating hurdles" for census work in the area.
But Samim Khpalwak, spokesman for the governor of Afghanistan's Kandahar province, said the Pakistani officials had strayed on to the Afghan side of the border and were attempting to count people living there.
"So far in the fighting, we have one Afghan civilian killed and three border police forces wounded," he told AFP, adding that the scuffle was still going on, with "dozens" of Afghan security forces rushing to the scene.
The two nations are divided by the "Durand Line", a 2,400-kilometre (1,500-mile) frontier drawn by the British in 1896 and disputed by Kabul, which does not officially recognise it as an international border.
Ethnic Pashtuns living along the border have traditionally paid it little heed, with villages straddling the frontier that have mosques and houses with one door in Pakistan and another in Afghanistan.
Border controls were virtually absent, and it was daily crossed with impunity by traders and travellers -- until recent clampdowns by Pakistan.
The border is not the only area of dispute between the neighbours: Afghanistan has long accused Pakistan of sponsoring the Afghan Taliban, though Islamabad says it provides the militants with safe haven as a "lever" to bring them to peace talks.
Pakistan has also accused Afghanistan of harbouring militants who carry out attacks in its territory.
Pakistan embarked on the enormous task of conducting its first census in almost two decades in March.
The fast-growing country is the sixth most populous in the world, with an estimated 200 million people, but has not held a census since 1998, despite a constitutional requirement for one every decade.