  In this paper, we introduce a class of singular integral operators which
generalize Calder\'on-Zygmund operators to the more general case, where the set
of singular points of the kernel need not to be the diagonal, but instead, it
can be a general hyper curve. We show that such operators have similar
properties as ordinary Calder\'on-Zygmund operators. In particular, we prove
that they are of weak-type $(1, 1)$ and strong type $(p,p)$ for $1<p<\infty$.
