Can the employer prevent the employee from resigning and hold his passport?

Dear Sir,

I've been working in a trading company under an unlimited contract for the last 10 months.

My contract which we both signed clearly mentioned that there will be 1 month notice period when I give my resignation.

I got a better job offer and now my employer is telling me that I can't step out of the premises without completing 2 months notice period and he is holding my passport too.

Could you please suggest to me what I can do?