Perpetrators trying to acquire our land illegally

My father bought a land in 2001 however just registration was done at that time and mutation was pending. In 2014 when we thought of selling the land, we got to know some other guy is claiming the land and he also sold a part of it to a third party. We did the mutation and tried to sell it but since they are local and the area is a bit remote and they have notorious allies, all potential buyers have been scared away. Now the 3rd party have started putting up pillars of bricks. We have tried all the ways from political help to doing 144 and caveat but nothing is working and he is keeping on the building process. We are not financially capable of filing a lawsuit. Please help us.