KARACHI, Pakistan

Tensions are running high between Pakistani and Afghan border forces after Islamabad shut its southwestern border with Afghanistan for cross-border movement for an "indefinite period," officials and local media reported on Monday.

The Chaman border – also known as Friendship Gate –, which connects Pakistan's southwestern Balochistan province to Afghanistan's southern Kandahar province, was closed after an armed Afghan reportedly crossed into Pakistan's border and opened fire on the security troops, killing a soldier and injuring another two on Sunday, Deputy Commissioner Chapman, Abdul Hameed Zehri, told reporters.

The attack was followed by hours-long firing between Pakistani and Afghan border troops, prompting the closure of the key trade border between the two neighbors.

Zehri said the border will remain closed until the handing over of the suspected attacker.

The two security forces, he added, are holding restraint since the firing was halted on Sunday night.

“The two sides are holding another round of flagship meeting today (Monday) to resolve the issue as we stick to our demand of handing over of the attacker,” a Pakistani security official told Anadolu Agency on condition of anonymity as he was not permitted to speak on the record.

"The Afghan officials have informed us that a search operation is underway to nab the attacker, who is still at large," the official added.

Footage aired on local broadcaster Geo News showed hundreds of trucks loaded with trade goods and other vehicles lined on both sides of the border, awaiting the re-opening of the crossing.

Thousands of citizens, mainly Afghans, who cross into Pakistan's bordering areas for medical and labor purposes, are also stuck.

Clashes between the two border troops, mainly at the Chaman border, have long been taking place, and there is no lull even after the re-capture of Afghanistan by the Taliban in August last year.

Pakistan and landlocked Afghanistan share 18 crossing points, with the busiest ones being the northwestern Torkham and Chaman border posts.

The two neighbors share a porous border of almost 2,670 kilometers (1,640 miles).