The bus left Bemina, Srinagar with 17 passengers, including four residents of Kashmir, visiting PaK to meet their relatives separated in 1947 due to partition, sources told UNI.
They said the bus has since reached Trade Facilitation Centre (TFC), Salamabad, Uri where more passengers will board it before leaving for Aman Post, the last Indian military post on this side of the LoC in Uri.
The exact number of passengers travelling to PoK will be known only in the afternoon they added.
The number of returnees and PaK guests will also be known in the evening, they said.
The bus service, introduced on April 7, 2005, despite opposition by militants, has helped thousands of families, divided due to partition, to meet each other.