Ambuja Cements, India's No.2 cement maker, said on Tuesday that it would buy a nearly 47% stake in rival Orient Cement for 37.91 billion rupees ($451 million), but analysts said there were doubts about the deal receiving regulatory approval.

Ambuja Cements Ltd., part of the Adani Group, has agreed to acquire Orient Cement Ltd. in a deal valued at 81 billion rupees ($963 million), as billionaire Gautam Adani continues to snap up makers of the key raw material needed for India’s infrastructure push.

Billionaire Gautam Adani's Ambuja Cements agreed to buy a 47% stake in Orient Cement in a deal valued at $963 million, stepping up acquisitions amid intensifying rivalry with tycoon Kumar Mangalam Birla.