State-owned Indian Oil Corp (IOCNSE -0.82 %) has emerged as the biggest bidder for city gas licences in the 10th bid round that also saw AdaniNSE -4.63 % Group, Hindustan Petroleum Corp Ltd (HPCLNSE -1.69 %) and Indraprastha Gas LtdNSE -2.78 % as the other prominent bidders, according to oil regulator PNGRB.