An armed conflict erupted once more along the border between Pakistan and Afghanistan after Afghan militants opened fire unprovoked, Pakistani officials said.

According to an official from Islamabad, Afghan forces began to fire at Pakistani positions late Wednesday night for more than an hour and Thursday morning renewed their attack.

Casualties were reported only in the Afghan camp, four soldiers being killed, but authorities from Kabul did not confirm the information.

The International Security Assistance Force sent a team in the region to investigate the conflict and reestablish peace.

Fire exchange consequently took place between the two countries, despite their adherence to the war against terrorism lead by the United States. The major problem for the two nations represents the large number of Taliban rebels and al-Qaeda members who carry out attacks in Afghanistan after crossing the border from Pakistan.

Pakistan is believed to be the training ground for most of the Taliban and al-Qaeda insurgents, many attacks on the border being staged by such individuals, sparking conflicts between Afghan and Pakistani forces.

A similar event occurred Monday, when two soldiers were killed after a man dressed as a Frontier Corps soldier opened fire on a delegation in the North-West Frontier Province. The delegation earlier took part in a meeting between Pakistan, Afghanistan and representatives of the coalition forces after heavy clashes on the border broke out.

The shooter hasn’t been identified, neither the group he belongs to.