Pakistani and Afghan troops exchanged fire at dozens of points along their border on Friday as the UN said their week-old conflict had forced the displacement of more than 100,000 people.The South Asian nations show no signs of rapprochement in their worst fighting in years, adding to the volatility in a region also contending with US and Israeli strikes on Iran — a country that borders both Afghanistan and Pakistan. Combat has included Pakistani air strikes on Taliban government installations such as the Bagram air base north of the Afghancapital, Kabul.Afghanistan’s Ministry of Defense said Taliban forces struck Pakistani military installations in more than two dozen locations along the 2,600-km (1,600-mile) border, destroying 14posts and shooting down a drone.