Afghan policemen keep watch on a military vehicle on the border between Afghanistan and Pakistan in Goshta district of nangarhar province in eastern of Afghanistan on May 7, 2013. Afghanistan summoned on Monday the Pakistani Charge d'Affaires and lodged protest over "unprovoked attack" on its forces earlier in the day. Pakistan on Tuesday summoned Afghan Charge d'Affaires and lodged a formal protest over the firing of Afghan forces which injured at least five soldiers, said the country's Foreign Ministry. (Xinhua/Tahir Safi)

Afghan policemen gather on the border between Afghanistan and Pakistan in Goshta district of nangarhar province in eastern of Afghanistan on May 7, 2013. Afghanistan summoned on Monday the Pakistani Charge d'Affaires and lodged protest over "unprovoked attack" on its forces earlier in the day. Pakistan on Tuesday summoned Afghan Charge d'Affaires and lodged a formal protest over the firing of Afghan forces which injured at least five soldiers, said the country's Foreign Ministry. (Xinhua/Tahir Safi)

An Afghan policeman keeps watch on a military vehicle with a machine gun on the border between Afghanistan and Pakistan in Goshta district of nangarhar province in eastern of Afghanistan on May 7, 2013. Afghanistan summoned on Monday the Pakistani Charge d'Affaires and lodged protest over "unprovoked attack" on its forces earlier in the day. Pakistan on Tuesday summoned Afghan Charge d'Affaires and lodged a formal protest over the firing of Afghan forces which injured at least five soldiers, said the country's Foreign Ministry. (Xinhua/Tahir Safi)

An Afghan policeman keeps watch on the border between Afghanistan and Pakistan in Goshta district of nangarhar province in eastern of Afghanistan on May 7, 2013. Afghanistan summoned on Monday the Pakistani Charge d'Affaires and lodged protest over "unprovoked attack" on its forces earlier in the day. Pakistan on Tuesday summoned Afghan Charge d'Affaires and lodged a formal protest over the firing of Afghan forces which injured at least five soldiers, said the country's Foreign Ministry. (Xinhua/Tahir Safi)