We develop a theory of microphase separation in a melt of flexible AB block copolymers with liquid crystalline side groups (C) attached to the B block using the strong segregation approximation. Within this theory, we analyze a case when all components of the system are strongly incompatible with each other. We predict thermodynamic stability of two kinds of cylindrical structures having amorphous and liquid crystalline cores, and four kinds of lamellar structures. One of the lamellar structures includes amorphous A and B layers having perpendicular orientations (so-called A 1 B lamellae). Three other kinds have parallel orientations of the layers. Depending on the Surface tension coefficient gamma(AC) of the AC interface, either combined BAB amorphous layers alternate with the smectic ones (BAB lamellae) or pure A and B layers are segregated by the smectic ones and their sequence looks like A-B-B-A-B-B... (A-B-B lamellae) or like A-B-A-B... (A-B-A lamellae). Phase diagrams of the system are constructed. Some of the results are compared with experimental data.