Berkshire Hathaway Chairman Warren Buffett walks through the exhibit hall as shareholders gather to hear from the billionaire investor at Berkshire Hathaway Inc's annual shareholder meeting in Omaha, Nebraska, U.S., May 4, 2019.
Berkshire Hathaway Chairman Warren Buffett walks through the exhibit hall as shareholders gather to hear from the billionaire investor at Berkshire Hathaway Inc's annual shareholder meeting in Omaha, Nebraska, U.S., May 4, 2019. Reuters / SCOTT MORGAN

Warren Buffett's Berkshire Hathaway Inc acquired nearly $1 billion of shares in Activision Blizzard Inc before Microsoft Corp agreed to buy the video game maker for $68.7 billion, according to a Monday regulatory filing.

Berkshire said that as of Dec. 31, it owned 14.7 million shares worth about $975 million of the "Call of Duty" maker.

Microsoft announced its plan to buy Activision Blizzard on Jan. 18, in its largest ever acquisition.

Activision shares are up 23% this year to $81.50, though they remain well below the proposed $95 per share takeover price, reflecting potential antitrust concerns.

Another prominent investor, Daniel Loeb's hedge fund Third Point, bought 2 million Activision shares in the fourth quarter.

Berkshire disclosed its Activision stake in a filing detailing its U.S.-listed stock investments as of Dec. 31.

Investors monitor Berkshire's investments closely to see where Buffett and his investment managers Todd Combs and Ted Weschler see value.

The filings do not say who bought and sold what, though Buffett generally handles larger investments.

Other media have quoted Buffett, a longtime friend of Microsoft co-founder Bill Gates, as saying he would not buy Microsoft shares because of potential conflicts of interest.

Gates ended his 16-year run on Berkshire's board in 2020. Buffett had been a trustee of the Bill and Melinda Gates Foundation but resigned in 2021.

In the fourth quarter, Berkshire also added to its stake in oil company Chevron Corp, while reducing its holdings in healthcare companies including Bristol-Myers Squibb Co and Abbvie Inc.

Apple Inc remains Berkshire's largest common stock holding.

Stock sales and Buffett's six-year drought in buying large whole companies have contributed to Berkshire's record $149.2 billion cash stake as of Sept. 30, 2021, despite at least $21.9 billion of stock buybacks that year.

Berkshire is expected to disclose more about its stock purchases, buybacks and cash on Feb. 26 when it releases year-end results and Buffett's widely read annual shareholder letter.

The Omaha, Nebraska-based company also owns dozens of businesses including the BNSF railroad, Geico auto insurance and Dairy Queen ice cream.