SAN FRANCISCO (MarketWatch) -- Berkshire Hathaway, the insurance-focused conglomerate owned by Warren Buffett, increased its stakes in Wal-Mart Stores and Wells Fargo during the third quarter, according to a regulatory filing Monday.

Berkshire took new stakes in Exxon Mobil , Nestle SA , Republic Services and Travelers Cos. during the period, the filing showed.

Berkshire sold shares of Eaton Corp. , Wabco Holdings , NRG Energy , Moody's Corp. and ConocoPhillips in the quarter, the filing also showed.

Buffett has generated strong returns over several decades, so changes in Berkshire's investment portfolios are closely watched. Monday's filing shows Berkshire holdings as of Sept. 30. It's likely that some of the company's investments have changed since then.

Berkshire's stake in Wal-Mart stood at 37,836,642 shares worth roughly $1.9 billion at the end of September, according to the filing payday loans online. That compares to 19,944,300 shares worth less than $1 billion at the end of June.

Berkshire increased its stake in Wells Fargo by more than 10 million shares during the third quarter, according to the filings.

Berkshire held 1,276,290 shares of Exxon Mobil at the end of September. Three months earlier the company held no shares of the oil company, according to the filings.

Berkshire held 3.4 million American depository receipts of Swiss food giant Nestle worth more than $144 million at the end of September.

The company's new stake in Republic Services was worth almost $100 million on Sept. 30, while its Travelers stake was worth roughly $1.3 million.

Berkshire raised Wal-Mart, Wells Fargo stakes