Houseing society parking issue

Our society has allotted 1 parking per flat to all. We love on 3rd floor and have a new tenant directly above us on 4th floor. Their now ours and theirs are 2 corner parkings which forms 2 sides of the building leaving a small space in between that legally doesn’t belong to any of us. For 10 years we were using that space to park our activa, cycle, 2nd car and there was never any problem. 2 months ago these people shifted here and started parking their 2nd car in that neutral space where we used to park our car because their landlord told them that neutral space belongs to them. We talked to them and The society association people told them to not park there but they didn’t listen. It became a race as to who came first will park their car there. I’m fact when we used to park our car there, they purposely park there car behind ours in such a way that we can’t take out our car without asking them to move theirs. We never harassed them in such a way. When they used to park their car in that space their car used to be half on the main road, and the only way to park the car completely in the parking was to park some of it in our parking space which they can’t do but we can. Yesterday, president of the society told them the same thing so now they’ve taken out their car but parked 1 bike and 3 bicycles there chained and locked with the pillar just so that we can’t park our car there. Please suggest how to go about this. I have taken pictures of their vehicles parked this way for proof. This is clearly a case of harassment and nothing else, they’re purposely doing this.