Reliance Industries, India's richest man, announced two acquisitions on Sunday, the latest move by the oil and retail giant to accelerate its foray into renewable energy.

Reliance announced earlier on Sunday that it would buy Norwegian solar panel maker REC Solar Holdings from China's Blue Star Group for $771 million. A few hours later, the company announced that it would buy a 40 per cent stake in Sterling & Wilson Solar Ltd, a solar company owned by Indian billionaire Pallonji Mistry, worth $372 million.

The two acquisitions will help Reliance's renewable energy division Reliance New Energy Solar expand in the global green energy market, including the US, Europe, Australia and the rest of Asia.

Ambani said at the annual shareholder meeting of Reliance Group in June that the company planned to invest more than $10 billion in the new business unit over three years, which would build solar modules, battery storage, electrolytic cells and fuel cell plants.