The two accidents happened back to back in Mastung district yesterday.
"Frontier Corp personnel were shifting the injured people of a road accident to hospitals in Mastung when their vehicle overturned in which three personnel were killed," a spokesperson of the Frontier corps (FC) said.
The first accident happened when a passenger coach that was going from Karachi to Quetta overturned in the Khad Kucha area of Mastung district, the spokesperson said.
"In that accident four passengers were killed while 30 were injured," he said.
"Unfortunately one of the FC vehicles also turned turtle due to rocky conditions and three soldiers were killed and the civilian driver was injured," the spokesperson said.