Judging by the fact that they are carrying Martini-Henry rifles (or just as likely Martini-Enfield rifles), I d say that they are either constabulary or local , Princely State forces. A number of Rajah's maintained their own forces, independent of the Indian Army. A number saw service in the Great War as Imperial Service Troops and they were usually equipped and armed with obsolete weapons, at least at the outset. The Indian Army at this time was equipped with SMLEs or in some cases older iterations of the Lee-Enfield.