* Berkshire invests $356 mln in digital payments firm - source
* Deal to value Paytm at more than $10 bln - newspaper
* Paytm counts Alibaba, Ant Financial and SoftBank as main backers (Updates with details, Google rebranding, adds comments)
By Trevor Hunnicutt, Sankalp Phartiyal and Kane Wu
NEW YORK/MUMBAI/HONG KONG, Aug 27 (Reuters) - Berkshire Hathaway Inc has acquired a 25 billion rupees ($356 million) stake in the parent of digital payments company Paytm, a source said, its first investment in an Indian startup as it moves into the financial payments sector.
The conglomerate run by billionaire Warren Buffett confirmed in an email that Berkshire had invested in One97 Communications Ltd. Buffett was not involved in the transaction, his assistant Debbie Bosanek said in the email, without giving more details.
India's Economic Times had reported here on Monday that Berkshire was in talks for a 3-4 percent stake in a deal valuing Paytm at more than $10 billion, citing people familiar with the matter.
The investment is a major endorsement for Paytm that has grown to become India's leading digital payments platform in just eight years.
For Berkshire, which is under pressure to find investments and whittle down a $108.6 billion stockpile of cash, this marks a rare shift in strategy. Buffett has traditionally invested in consumer, energy and insurance companies.
The foray into India's ultra-competitive digital payments space is not without risks. The market is expected to grow five-fold to $1 trillion by 2023, but rivalry is intense, with several players - including the state-backed Unified Payment Interface (UPI), in the fray.
Unlike digital wallets, which do not earn users any interest, UPI apps simplify interbank transfers, making it a preferred option for some.
Paytm and other mobile wallet companies have been forced to offer more services to retain customers.
Google earlier rebranded its Tez app as Google Pay, adding that it was teaming up with four top Indian banks, including HDFC Bank and ICICI Bank, to offer instant, pre-approved digital loans to customers.
"Google has more Internet users' data than any other tech company so they can work with banks to offer solutions to these customers," said Satish Meena, senior forecast analyst at Forrester Research.
"Google's partnership with Indian banks to offer loan products is going to be a challenge for Paytm and even WhatsApp, which is yet to formally launch its payments service."
In May, Buffett had indicated an interest in the financial payments industry at an annual shareholders meeting, saying the sector was a huge deal around the world and that many companies were working to reinvent the space.
One of Buffett's investment deputies, Todd Combs, seen as a potential chief investment officer at Berkshire, was leading the Paytm deal and has been given a seat on its board, the company said on Tuesday.
Combs has also led Berkshire's efforts to start a healthcare joint venture with Amazon.com Inc and JPMorgan Chase & Co.
Paytm, founded by Vijay Shekhar Sharma in 2010, counts China's Alibaba Group and its financial services arm Ant Financial Services Group among investors.
Alibaba and Ant Financial, which runs China's top payment system Alipay, jointly own about 40 percent of Paytm's parent after an investment in September 2015, Reuters has reported.
Japan's SoftBank also became a shareholder in May 2017, injecting $1.4 billion in Paytm's parent company for a 14.2 percent stake and some existing shares. That investment would value Paytm at about $7 billion.
One97 Communications and SoftBank did not respond to requests seeking comment. A spokeswoman for Alibaba referred Reuters requests to Paytm.
($1 = 70.16 Indian rupees)
Reporting by Trevor Hunnicutt in New York, Sankalp Phartiyal in Mumbai and Kane Wu in Hong Kong; Additional reporting by Brenda Goh in Shanghai, Swati Bhat in Mumbai, Mekhla Raina in Bengaluru; Editing by Gopakumar Warrier, Steve Orlofsky and Louise Heavens