When two or more persons agree to do, or cause to be done,--

(1) an illegal act, or

(2) an act which is not illegal by illegal means, such an agreement is designated a criminal conspiracy:

Provided that no agreement except an agreement to commit an offence shall amount to a criminal conspiracy unless some act besides the agreement is done by one or more parties to such agreement in pursuance thereof.

Explanation.--It is immaterial whether the illegal act is the ultimate object of such agreement, or is merely incidental to that object.]