You can find a briefcase on the roof of one of the clay huts at Dogon Village. To get to it, you'll need to jump onto a straw shelter (to the north-west), from there onto the roof of a hut, from there onto another straw shelter and then to the roof with the briefcase on it. Refer to the smaller image for the initial shelter you need to get on to.
At the north-western side of Dogon Village you can find a passage (with stairs) moving up the cliff; it soon splits it two - take the right path (going north) and you'll come to a small cave with a briefcase inside.
West of Outpost you can find a dense collection of clay huts. There's a briefcase on the roof of one of them - to get to it, get onto the nearby rock (see smaller image) and jump onto the straw shelter - and from there onto the roof.
There's a large sign near the road right by the border in the northern part of the region. Right by the sign sits a briefcase. Notice the irony of the scenery - the sign is a commercial for a water company, and in front of the sign lies a dead soldier with a water bottle nearby. How tragic ;o)
In the south-western part of the region you'll come upon a small pond with massive cliffs to the west and north. On the western side of the pond you'll notice a large rock - behind the rock sits a briefcase.
You'll find a hut with some wooden stairs (or ladder) going up to the roof. On the roof, you'll find a hole covered with planks. Destroy the planks and drop down through there hole where you'll find a briefcase.
Inside a small cave (or crack) in the large rocks on the eastern border of the region you can find a briefcase sitting on what appears to be a weapons crate. Go around to the eastern side of the rocks to find the entrance.
On the northern side of the cliffs that are north of Sediko you can notice a small shelter up on an elevated area; a fallen ladder lies nearby. A briefcase is located at the shelter. To get up there, use the Hang glider that you can find near the Antenna to the north.