Can I resign if salary is withheld without any notice

I have resigned from my post as I got a better opportunity. I have 3 month notice period which I wanted to buy but my employer did not give me the receipt of same and asked me to withdraw as there will be huge loss to company and asked me to finish the year and then leave. So I wrote a withdrawal letter. Now my employer started to harass me by making me write the withdrawal letter again and again. More over, they stopped my salary without any written clarification. Though I asked via email many times but of no use. Now, I want to discontinue immediately with three months notice. Now my employer is threatening me that he will not give me my original certificates (which the kept with them from the time I joined i.e. 3 years) and the experience certificate as I did not serve till the end of year as mentioned in appointment letter. My question is if they don't pay me salary without any notice then should I have to abide by the appointment clause and can they withheld my certificates and service experience? Please help!