This article addresses the problem of efficient multi-robot patrolling in a known environment. The proposed approach assigns regions to each mobile agent. Every region is represented by a subgraph extracted from the topological representation of the global environment. A new algorithm is proposed in order to deal with the local patrolling task assigned for each robot, named Multilevel Subgraph Patrolling (MSP) Algorithm. It handles some major graph theory classic problems like graph partitioning, Hamilton cycles, nonHamilton cycles and longest path searches. The flexible, scalable, robust and high performance nature of this approach is testified by simulation results. Categories and Subject Descriptors G.2.2 [Discrete Mathematics]: Graph Theory — Graph algorithms; Path and circuit problems; I.2.8 [Artificial Intelligence]: Problem Solving, Control Methods, and Search — Graph and tree search strategies; Heuristic methods; Plan execution, formation, and generation.