Global agency Moody's Investors Service said it had affirmed Reliance Industries' Ba2 ratings for senior unsecured debt securities, but changed the outlook to negative from stable.

In a statement released on Monday, Moody's said the change in outlook reflected concerns about the Reliance group's recent aggressive expansion.

Reliance Industries is the nation's biggest petrochemicals maker and a leading refiner. Last month, group company Reliance Infocomm announced it had launched limited radius mobility services.

Observing that Reliance's recent expansion was "significantly outside its well protected, strong margin petrochemical business," it said, "Moody's believes that this rapid expansion into liberalising and more competitive markets will lead to weaker profitability and operating cash flow margins."

It cited refining and telecom operations in particular as reasons for weaker operating cashflow margins and said that expansion at the same time would increase the investment levels.

"It is unclear at this stage how much of the financing for these various investments will be taken on Reliance Industries' balance sheet," the statement said while clarifying that the group's telecommunication companies -- Reliance Infocomm and Reliance Telecom -- are only treated as non-consolidated associate investments.

It also wondered as to how much would be debt-financed via Reliance Industries associate companies and how much would be provided by strategic or financial partners.   

RIL is the top private corporate in India, having interests in chemicals, polymers, fibres and oil refinery with growing interest in telecommunications and power generation.

RIL has generated a consolidated turnover of Rs 5,710 crore (Rs 57.10 billion).

Additional inputs: PTI