Employer refuses to pay overtime for weekend work - is this legal?

I’ve been working for a tech company in Bengaluru, and recently, they’ve asked us to work on weekends due to a project deadline. However, they aren’t paying us any overtime for these extra hours. When I asked HR about it, they said it's part of the job expectations. I feel this is unfair, as it’s eating into my personal time. Is this legal under Indian labor laws? Should I be getting paid for this additional work?