Shares of UnitedHealth Group are surging before the market open Friday as Warren Buffett's Berkshire Hathaway disclosed that it recently purchased shares of the beleaguered insurer. Berkshire Hathaway bought around 5 million shares of UnitedHealth last quarter,

Warren Buffett's Berkshire Hathaway has acquired 5 million shares in UnitedHealth Group , a regulatory filing showed on Thursday, sending the health insurer's stock up 7% in extended trading.

UnitedHealth shares jumped 10 per cent in pre-market trading on Friday after Warren Buffett’s Berkshire Hathaway snapped up a stake in the troubled US healthcare group. The new investment, worth $1.6bn at the end of June, was disclosed in a filing late on Thursday detailing changes to Berkshire’s $268bn stock portfolio during the second quarter.