Landlord entered my Pune flat without permission and changed locks?

I'm really stressed! I live in Pune and my landlord entered my flat without notifying me and changed the locks while I was away for work last weekend. I’ve been living here for 3 years and never had issues before. I tried calling him but he’s not answering. My belongings are still inside. I don't know what to do. Isn’t this illegal? How can I regain access to my flat? Should I approach the police or seek a legal order? Please help!