Image: Stuart Isett Image: Stuart Isett

Billionaire investor Warren Buffett has revealed that his investment firm recently purchased a $1 billion stake in Apple.

Apple's shares have suffered over the past year, with investors concerned that the tech giant will not be able to maintain its profit growth after iPhone sales fell for the first time. In fact, at one point last week Apple lost its place as the world's most valuable company when it dipped below Google's parent company, Alphabet.

But Buffett is known for buying "value stocks" - meaning this purchase is being seen a major win for Apple.

However, the Wall Street Journal disputes its significance because it was Buffett's firm, Berkshire Hathaway, that bought the shares, rather than the man himself. Typically an investor that has stayed away from tech companies, WSJ said two members of Buffett's Berkshire Hathaway team, Todd Combs and Ted Weschler, are much more willing to invest in tech firms and would have decided to buy shares in Apple.