Employer Demanding For Compensation After Termination

I had been working for last 3.5 years with my past employer. They had terminated me on immediate effect claiming my Misconduct behavior which includes demanding for pending salary, provident fund facility implementation, etc. And now after 15 days of termination they have issued me a Legal Notice claiming for compensation amount in lakhs because they faced financial loss in my absence.
So please help me. Should I worry or not and with what steps should I proceed?

You should immediately contact a lawyer with all documents and give reply to the said notice.
Whether you need to worry or not is matter of studying your case but giving a reply to the notice is important.

Any one can suggest only after reading your termination letter and thereafter claim letter . But
If they forcefully terminated without show cause or charge sheet or domestic inquiry , you take help from any trade union leader/advisor and file a case before labour court for illegal termination and ask to reinstatement with full back wages.

Probability is that they might not have followed the due procedure before terminating your services on the ground of misconduct. Realizing it later and scared of any legal redress from your side, as a pre-emptive move your ex-employer might have issued such a notice for damages. Simply send a reply through a Lawyer denying all the allegations. Raise a dispute under Sec.2 A (1) of the Industrial Disputes Act,1947 before the Labour Officer for the area,if you are a workman. Otherwise, file an appeal against the orders of dismissal before the Appellate Authority under the State's Shops and Estt Act, if the establishment is covered by the Act or institute a Civil Suit claiming damages for wrongful termination with the assistance of a Service Advocate.