Billionaire U.S. investor Warren Buffett is taking advantage of depressed share prices during the economic downturn, investing 3 billion Swiss francs ($2.6 billion) in the world's second largest insurer Swiss Re.

The investment, which amounts to a 20 percent stake in Swiss Re, is being done through Buffett's diversified conglomerate Berkshire Hathaway Inc which also owns major U.S. insurance firm Geico.

American Depositary Shares of Swiss Re trading over-the-counter have fallen sharply over the last year. In April shares reached a high above $92 each. At the close of trading Thursday, shares were at $25.79.

Swiss Re is struggling as the economic crisis hits, also announcing it will cut bank on some of its business, saying it will end its financial markets activities including securities trading. Last year that activity resulted in a loss of 6 billion, according to Bloomberg.

We are disappointed with our overall results, said Swiss RE's chief executive Jacques Aigrain said in a statement. Warren Buffett's agreement to invest in Swiss Re is a testament to the strength of our franchise.

Swiss Re is expected to announce its full-year results on February 19.