The collaborative navigation of a team of ground mobile robots in an unknown planar environment towards fixed stationary targets is the subject of this paper. Each mobile robot is equipped with a limited field of view limited-range finder and a magnetometer to infer its orientation. Each target location is known, and a switching objective function initially guarantees the individual robots exploration towards its target area and afterwards safely guides each robot towards its target. During the collective exploration, the robots exchange their maps in a collaborative manner. If a robot detects the target that is assigned to another robot, it communicates this information to the corresponding robot and continues to explore its target. The other robot rather than performing exploration towards its already discovered target, it attempts to join its map with that of the reporting robot. Simulation results that prove the efficiency of the proposed scheme are presented.