American billionaire Warren Buffett's Berkshire Hathaway group has officially become the top shareholder in Bank of America after exercising its right to buy 700 million shares at a discount.

Buffett had received the warrants in 2011 after investing $5 billion in the bank, which was suffering at the time from the fallout from the global financial crisis. 

Bank of America said Buffett had acquired the shares for about $7.14 each -- well below their Tuesday closing price of $23.58.

Buffett's investment is now worth $16.51 billion, meaning he has made a capital gain of nearly $12 billion.

"In 2011, we welcomed Berkshire Hathaway as a shareholder, and we appreciate their continued support now as our largest common shareholder," the bank's CEO Brian Moynihan said in a statement.

Buffett's other holdings include major assets in real estate and insurance. He is also the biggest shareholder in Wells Fargo.

Source: AFP