Illegal Occupation of Land

Hi, I am working abroad. I have a (30x40) corner-site in Bengaluru to build a house on. One party sold my subject site to a third party by a word-of-mouth without making sure that the subject site belonged to him! The site is registered in my name, and the party who bought the site has nothing to claim (he has no registration papers at all!). The buyer constructed a (factory-type) house over the site. I failed to understand as to how he got the plan sanctioned to build the house since he had no documents whatsoever to apply for the plan. May be the selling-party had given him the authority to build the house without legally applying for the plan, which is considered as completely illegal (illegal construction)l! In fact, the selling-party was owning a similar site but at a little distant place in the same locality. According to him, he mistakenly understood that the site in question had belonged to him. Upon complaining about the issue to the party who bought the site, he told me that he has settled the site value to the selling party, and accordingly, upon checking/complaining about the issue to the selling party, he is offering and compelling me to get registered his above-referred site, the actual location and the site value of which are completely different. I rejected his offer and asked (insisted rather) for returning the possession of the land. Finally, the selling party promised me that he will give me the value of the land which I agreed. The follow-ups have been there for the promised site-value since four years, and he is just giving one or the other excuses, repeating each and every time the same words “I will settle the money soon, give me some time”. I am totally fed-up with his false promises! I would have started the legal proceedings a long back, but since I am working abroad, I am finding it difficult to do the same. Because of the hard times the selling party has given to me since 4 years, I want a tip/assistance as to how I can start the legal proceedings against the land-occupier. In brief, I want to know as to how I can start the legal proceedings against the selling-party or the land-occupier (buyer) by being abroad in order to get back my land, where I do not have any relative to give the authority, such as, GPA. Thanking you for the kind and valuable guidance/assistance in advance. Sincerely, Syed Altaf