Termination without notice or warning

In legal terms, there is nothing like "asking you to leave or resign". Either the employee resigns or the employer terminates his service. 

If you resign yourself for whatever reason, you cannot challenge such termination. 

If they terminate you, can can surely challenge it. Terminating someone on the ground of non-performance requires to issue charge sheet, conduct domestic enquiry and prove such alleged non-performance of the employee. In your case nothing has happend. 

Hence, you challenge the termination asking for reinstatement and also to pay the outstanding salary. Once you accept such termination, even though illegal, you can claim for full and final settlement including dues like gratuity, if applicable.

It is advisable that before taking any steps, you contact a labour law advocate with all relevant documents. 

Did you record the demand of resignation or threats etc (audio/visual/witnessed/minuted)?

The onus may fall on you to prove.

Termination is a speaking order.

Since you have been asked to remain out of office, and that you shall be communicated the decision,you could have minuted it at least.

If you are being relieved then it is based on what; resignation, termination etc?

Under performance/Non Perfromance is not  a misconduct. Employer should provide training and suport to improve the performance. 

However now you may approach an able counsel specializing in labor-service matters and proceed further under expert advise of your counsel.