Can my employer terminate me during my sick leave under esi sick leave

I have a serious consern that my employer terminated me just after i joined back from my esi sick leave. I was on leave from 1month i joined on April 1st and they terminated me on 4th saying very arrogant and abusive that i was not productive last month. Can i sue them .do we have any esi legal acts for such people.

Termination has to be done following due procedures.
System of review of productivity of each employee should be public onowledge of employees being assessed.
Targets,quality,no: of products rejected by QC etc.
They should not suddenly out of the blue state poor productivity etc and terminate.
From bare details given by you,apparently termination is nor in accordance with prinicples of natural justice.
Take up the matter with higher management in factual manner in writing by Speed Post for acknowledgement sake.
Take advice of a lawyer who deals in HR matters.