Illegal claim on my plot by my neighbours

5 yrs back We have constructed a house on our plot in UP. During the construction our neighbours force fully constructed a wall touching the rear side wall of our house with help of village people. because we stay in mumbai the neighbours started ploughing our land located at left side of our house and planted a mango tree in front of our door. Now the plot being 10 feet below the ground level we want to fill mud and open the door now the neighbours are not allowing us to throw mud and open the door. Please guide what can we do now because we have no option left and our work has been stopped.