Omnicom Group Inc, the world's second-largest advertising company, has agreed to pay 1 billion reais ($270 million) for Brazil's Grupo ABC, growing Omnicom's publicity, branding services and content in Latin America's largest economy, said a source with direct knowledge of the transaction on Friday.

Grupo ABC's founding partners Nizan Guanaes and Guga Valente agreed to stay with the company for five years, said the source. Under terms of the deal, its value could change at the end of that period because of performance, said the source, who requested anonymity because the deal remains private.

Omnicom agreed to pay for Grupo ABC, the largest Brazilian diversified advertising firm, around 15 times tthe annual operational earnings at the São Paulo-based company, said the source. According to Reuters intelligence data, this might be the largest industry deal in Brazil since at least 2008.

A spokesman for Grupo ABC declined to comment. A message left on the office phone of Omnicom's media relations office was not immediately answered.

New York-based Omnicom is growing in Brazil amid mounting interest from global giants in Brazil's advertising market, Latin America's largest. Last year, Omnicom scrapped a merger plan with French rival Publicis Groupe SA, which has grown in Brazil with the purchase of DPZ and other assets.

Grupo ABC was founded by Guanaes and Valente in 2002, and over the years attracted Kinea Investimentos Ltda, a private equity firm controlled by Itaú Unibanco Holding SA, and investment firm Grupo Icatú SA as partners. The source did not elaborate how the purchase would be made.

Grupo ABC was advised by Itaú's investment-banking unit, while Moelis & Co worked for Omnicom in the transaction, said the source.