According to the source, Pakistani soldiers opened fires after 10 Afghans crossed the border via a dirt road near the checkpoint.
Bodies of the killed Afghans still lie near the checkpoint, the source added.
Earlier, the United States and NATO asked Pakistan to facilitate the evacuation of foreign citizens from Kabul, according to a source in the Pakistani foreign ministry.
Following a weeks-long offensive launched after the US started withdrawing forces from Afghanistan, the Taliban entered Kabul on 15 August and caused the civilian government to fall. This prompted thousands of locals to seek escape for fear of reprisals from the militants. Many countries have since begun evacuating their diplomatic missions and citizens from the Central Asian nation.
*A terrorist group outlawed in Russia and many other countries.