According to tribal sources in Kurram Agency, the attack happened at Lakka Teega area of Lower Kurram Agency, which connects Kurram and North Waziristan agencies of the tribal belt with Khost province of Afghanistan.
"Troops were carrying out routine surveillance along Pak Afghan border for plugging of gaps and making necessary preparations for starting fencing in that area", it said.
Two of them died and five others were wounded, it said in a statement, without confirming if the Pakistani security forces also opened fire. Following the announcements, several armed tribesmen, belonging to Toori Bangish and other tribes started approaching the border posts.
Earlier in April, Afghanistan accused Pakistan of conducting the air strikes and firing hundreds of shells in Afghan's eastern border province of Kunar. A local political official, who asked not to be identified, said that Pakistani security forces had responded on Sunday by opening fire along the border. "Mil [military] engagement is underway to defuse situation", the ISPR said in a statement.
Initially, Afghan National Police interim chief Colonel Abdul Hanan told Anadolu Agency that two Pakistani troops were arrested during the clash.
Several Afghan soldiers including a policeman and a local tribesman were killed in the ongoing clashes with Pakistan's paramilitary Frontier Corps near the disputed border Durand Line on Saturday.
Afghan officials often give conflicting casualty figures.
Kabul has long-accused Islamabad of providing safe havens for the Afghan Taliban, which has been waging an insurgency in Afghanistan for more than 16 years. It was once an ideal point for militants to move across the border in the past.