Employer terminated me after 12 years of service with no severance?

I worked as a senior manager with a company in Mumbai for 12 years. Last week, they suddenly terminated me without any prior warning or notice period, citing company restructuring. They have not offered any severance or compensation. I am 48 and finding it difficult to get another job quickly. Is this legal under Indian labor laws? What steps can I take to challenge this and get my rightful dues?