Aug 14 (Reuters) - Warren Buffett's Berkshire Hathaway ( BRK/A )

disclosed on Thursday that it has begun investing in

UnitedHealth Group ( UNH ) after the insurer became a target for

many Americans upset over the direction of the nation's

healthcare.

Berkshire said it owned 5.04 million UnitedHealth ( UNH ) shares

worth about $1.57 billion as of June 30.

Buffett's conglomerate also said it sold 20 million shares

of Apple ( AAPL ), its largest stock holding, in the second

quarter, reducing its stake to 280 million shares.

Berkshire also revealed it has bought the common stocks of

security products provider Allegion ( ALLE ), home builder DR

Horton ( DHI ), outdoor advertiser Lamar Advertising ( LAMR )

and steel maker Nucor ( NUE ), and significantly increased its

stake in homebuilder Lennar ( LEN ).