Head to the camp and identify your targets using your camera. You have to make stealth kills to remain undercover. Of course, you have to kill them without anybody seeing you. The first VIP will move up the ramp past the two snipers. Follow him there and kill him without any problems.
Continue upstairs to find the second VIP near the ledge. The last VIP is inside the cave. You have to kill the soldiers behind him to prevent them from being alarmed. After killing them all leave the camp and head to the marked location to complete the mission.