If there is nothing in the employment contract, it does not mean you cannot resign with immediate effect. Lets see what the law says. The following section of the Employment Act is quite clear about that:
"13. Termination of contract without notice.
(1) Either party to a contract of service may terminate such contract of service without notice or, if notice has already been given in accordance with section 12, without waiting for the expiry of that notice, by paying to the other party an indemnity of a sum equal to the amount of wages which would have accrued to the employee during the term of such notice or during the unexpired term of such notice,"