Can my employer in Bangalore force me to work overtime without pay?

I recently joined a tech company in Bangalore. My contract does not mention mandatory overtime, but my manager insists that I stay late frequently, stating it's part of the 'company culture'. They are not offering any additional compensation or time off in lieu. I'm worried because I can't keep up with these demands due to personal commitments. I feel this is unfair and I'm stressed about losing my job if I refuse. Is it legal for them to enforce unpaid overtime like this? What rights do I have to refuse without facing repercussions?