Professor2know:

Promise Jane,

You need to fulfill the requirement of your prospective employer. However, how on earth can you send a cv without a covering letter? Some Nigerian graduates blow their chances away writing covering letter without the cv or vise versa. The painful thing in it is that some graduates don't know how to write a simple formal application letter. Some even abbreviate un-necessarily and commit series of grammatical blunders to discourage their employers.

In summary, I think, in my oppinion, both should go hand in hand except the prospective employer specifies otherwise.