In my company contract it's mentioned that during training period either party can terminate the contract without serving notice period but when I submitted my resignation letter my HR is saying to serve notice period of 10 days. Now what can I do?

Do share the highlighted part of the contract over mail with HR, and make sure to document everything along with it keep a copy in your personal email ID (you can Bcc yourself or click a picture).

First check the date of joining in relation to training period tenure, and go through your contract again to make sure that it's still valid and there are no hidden details. If all is correct, you refuse to serve notice and stop coming to the office after handing all assets. Do share the highlighted part of the contract over mail with HR, and make sure to document everything along with it keep a copy in your personal email ID (you can Bcc yourself or click a picture). The firm cannot force you or sue you if everything is inline with the contract. It will not hold legally in case they decide to take action, and if they hold your training or relieving letter, you can take a legal action.