MUMBAI: India's competition regulator has launched a surprise raid on several advertising behemoths, including GroupM, Dentsu and Interpublic Group, as well as a broadcasters' industry body over allegations of price-fixing, sources with direct knowledge told Reuters on Tuesday.

The Competition Commission of India's officers descended upon roughly 10 locations in Mumbai, New Delhi and Gurugram after initiating a case against the agencies and top broadcasters for allegedly colluding to fix advertising rates and discounts.

The raids come at a pivotal moment for India's advertising landscape, which is experiencing significant upheaval following the $8.5 billion merger between Walt Disney and Reliance's Indian media assets.  This regulatory blitz also follows hot on the heels of Omnicom Group's $13.25 billion all-stock acquisition of rival Interpublic Group in December, a deal that created the world's largest advertising agency.

According to one source who spoke to Reuters, the watchdog is investigating how advertising agencies allegedly conspire with certain broadcasters to fix advertising prices when selling to clients, including discussions around discounts. The allegations reportedly include concerns that certain broadcasters engaged in "collective action" to avoid offering discounts on advertising rates.

The Indian Broadcasting &  Digital Foundation (IBDF), which represents heavyweight domestic broadcasters including billionaire Mukesh Ambani's Reliance-Disney joint venture and Sony and Zee, has remained tight-lipped about the investigation.

Representatives from GroupM (owned by Britain's WPP), IPG Mediabrands and Japan's Dentsu all declined to comment when approached by Reuters, as did the competition commission itself, which maintains a policy of not publicly disclosing details of enforcement actions or price collusion cases.