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.

Warren Buffett's Berkshire Hathaway increased its holdings in UnitedHealth Group stock, and also added positions in D.R. Horton, Lamar Advertising, and Nucor.

Berkshire Hathaway acquired about 5 million shares of UnitedHealth Group Inc. in the last quarter making a stake of about USD 1.6 billion in the company. Reportedly, the stake puts UnitedHealth at the 18th-largest position in the portfolio of Berkshire.