This paper addresses robust control of multiple mobile robots moving in desired formations. A rigorous control technique for such an agent-based robotic system may encounter problems of singularity, parameter sensitivity and inter-robot collision. Our proposed framework focuses on the enhancement of robustness as well as collision-free establishment of formations even in the case of singularity and uncertainties in sensing information of the reference coordinates by using variable structure controllers incorporated with a reactive control scheme. Advantages of the approach are verified in simulation of three robots moving in a line, a column and a wedge.