UnitedHealth Group Inc said on Wednesday that its board had significantly increased the health insurer's stock buyback program.

UnitedHealth may now repurchase up to 120 million shares, including about 23 million remaining under a previous buyback program. At Tuesday's closing price of $33, buying back 120 million shares would equate to nearly $4 billion.

UnitedHealth bought back 74 million shares in 2009 at a weighted average purchase price of $24.26 each.

The company had about 1.15 billion common shares outstanding as of December 31.

UnitedHealth's board also authorized an annual dividend of 3 cents per share, to be paid in April. The company paid a 3-cent-per-share dividend last year.

(Reporting by Lewis Krauskopf; Editing by Lisa Von Ahn)