At least four Pakistani soldiers were killed on Sunday in a rocket attack in a tribal area of Khayber-Agency that borders Afghanistan, the military’s media wing reported.The Inter-Services Public Relations said the rocket fired by terrorists from Afghanistan also injured four others.This is not the first time a cross border attack has happened on the Pakistan-Afghan border.The attack comes at a time when relations between Islamabad and Kabul have deteriorated in the wake of a surge in Taliban attacks in Afghanistan and statements of Afghan leaders against Pakistan.Pakistan earlier summoned the Afghan ambassador to lodge a protest over a border clash in which three Frontier Constabulary men were killed on August 16-17.