By Carolina Mandl and Sittrarasu S

NEW YORK/BANGALORE (Reuters) -Warren Buffett's Berkshire Hathaway Inc reduced its stakes in Activision Blizzard and in Bank of New York Mellon in the fourth quarter, while it added shares in Apple Inc, according to a regulatory filing on Tuesday.

The move by Berkshire comes as Microsoft Corp makes efforts to conclude its acquisition of Activision Blizzard, maker of the "Call of Duty" video game. On Feb. 21, Microsoft will defend the deal in front of European Union and national antitrust officials at a closed hearing.

Berkshire reduced its stake in Activision Blizzard by 12.35%, and now holds a 6.7% stake, or 52,717,075 shares, according to the filing.

Berkshire also trimmed its stake in BNY Mellon by roughly 60% in the last quarter, to 25.1 million shares. At current prices, it represents roughly $2 billion in shares of the bank sold.

On Apple, Buffett's company bought another 20.8 million shares, or $3.2 billion, bringing his stake to 5.8% in Apple, which Buffett considers more as a consumer products company, according to the filing.

(Reporting by Carolina Mandl in New York; editing by Jonathan Oatis and Leslie Adler)