ASADABAD: The border between Kunar in Afghanistan and Mohmand in Pakistan is irrelevant for the people who live there, and regularly criss-cross it on a dirt road, but for troops fighting in the area it is a dangerous and confusing line in the sand.

Densely forested and lightly populated, the area is a haven for Taliban insurgents targeting the armies of both nations, and who put the border their enemies cannot cross to great tactical use.

Confusion about who was firing, and from where, may have contributed to a Nato air attack on a Pakistani border outpost on Saturday, that killed 24 soldiers.

Western and Afghan officials say there was cross-border fire before air support was called in; the Pakistani army denies this and says the attack was unprovoked.

Afghan Taliban commanders, who have been known to fire from near army bases and civilian homes to hinder their targets' response, said they were not operating in the area that evening.

People from the Mohmand tribe live on both sides of the ill-marked border with Pakistan, that the Afghans call “Point Zero”, but pay little heed to. They pass through it daily on a dirt track, without passport or ID, for business or to see relatives.

They also watch waves of militants wash by in both directions, pursued by soldiers who have to stop at wherever they think the border is; not always the same for Afghans and Pakistanis.

“When there is an operation from the Pakistani side, the Taliban flee into Afghanistan and when Afghan and foreign troops conduct operations, the insurgents flee into Pakistan,” said influential Mohmand tribal leader, Abdul Wahed Khan, reached by phone from Asadabad, the capital of Afghanistan's Kunar province.

At the southern edge of Kunar, the border region is a rough, and sometimes lawless place, where locals who are mostly farmers and shepherds carry both weapons and mobile phones, but have to trek up to mountain tops to get a signal.

Timber is a huge business but dominated by the Taliban and their supporters, who fell trees and smuggle them into Pakistan.

WHERE IS THE BORDER?

The border is supposed to be marked by the Durand line, named after a British colonial administrator who helped decide its course in the late 19th century.

But it has been contested almost since it was laid down, and the wilder mountain areas it is both unclear and ignored by locals.

For the soldiers fighting there, Afghan, Pakistani and from the Nato-led coalition, the confusion can be deadly.

“The border is in dispute. I mean this is the Durand line, and when ... you lay out maps of where the border is, there will be differences of multiples of kilometres, in some cases even a five kilometre difference, in where the border is,” one senior alliance official, who requested anonymity to discuss sensitive border issues, said recently.

Pakistani outposts have been creeping closer to where Afghanistan thinks the border lies over three decades of war, said Khan, the Mohmand tribal elder.

Decades ago, when Pakistan's tribes and army were backing the Mujahideen battling the Soviet Army, they had the support of many locals for setting up nearby combat posts, but some Afghans now fear their territory is being annexed.

“Pakistani troops this year have moved up their outposts closer to the borderline which has created problems for us,” said a senior Afghan border policeman, who suggested the Nato attack was in a grey area that once belonged to Kabul.

“I can't really say that's part of Afghanistan because that area where the operation took place is under the control of Pakistani forces,” he told Reuters, adding that the outposts were unusually well-built concrete ones.

The Pakistani post that was attacked was just 200 metres (yards) inside the country, Pakistani security officials said, in an area that many villagers have fled after years of fighting.

The mountainous terrain means the soldiers rarely leave their camps, even though the Pakistani Taliban, who briefly controlled parts of the area in 2007 and 2008, have bases across the border and regularly stage attacks from there, the security forces said.