•A system is proposed to obtain heterogeneous rocks with irregular inclusions.•Realistic inclusion geometry is obtained and controlled by combining the circular parameterization and Fourier transformation.•An unique overlapping detection algorithm based on level-set function is developed to allocate inclusions.•Hydraulic fracturing are captured by integrating cohesive pore pressure elements into traditional finite element model.•A systematic hybrid finite-discrete approach for investigating hydraulic fracturing of heterogeneous rocks is proposed and validated. A systematic hybrid approach for modelling the hydraulic fracturing process of heterogeneous rocks with irregular inclusions is developed. This approach is based on a series of computational algorithms, including Fourier series transformation, level-set-based overlapping detection, and the finite-discrete element method. Three major steps are included: (1) circular parameterization and Fourier transformation are employed to reproduce realistic inclusion contours with arbitrary irregular shapes; (2) a novel overlapping detection method based on a level-set function is employed to allocate irregular inclusions effectively and efficiently; and (3) the finite-discrete element model is established by integrating cohesive elements with pore pressure nodes into the solid mesh to simulate the progressive hydraulic fracture and interface crack of heterogeneous rocks. To validate the proposed hybrid approach, modelling results by the established model are compared with numerical simulations in the literature. In addition, the influences of injection speed and interface strength on the mechanical and fracturing responses of heterogeneous rocks are discussed. The results demonstrate that the proposed hybrid approach is capable of simulating the hydraulic fracturing process of heterogeneous rocks.