UPDATE 1-Walgreens tops profit estimates, authorizes share buyback

(Adds details on profit, background on Rite Aid stores)

June 28 (Reuters) - Walgreens Boots Alliance Inc's third-quarter profit beat analysts' expectations on Thursday, benefiting from its acquisition of Rite Aid Corp stores, and the drugstore chain authorized a $10 billion share buyback program.

Walgreens scrapped its deal to buy Rite Aid outright last year after failing to win antitrust approval, and said it would instead buy some of the smaller rival's U.S. stores.

Net income attributable to Walgreens rose 15.5 percent to $1.34 billion, or $1.35 per share, in the third quarter ended May 31.

Excluding items, the company earned $1.53 per share, beating analysts' expectations of $1.48 per share, according to Thomson Reuters I/B/E/S.

The company also said it had increased its quarterly dividend by 10 percent to 44 cents per share.

Sales at Walgreens' U.S. pharmacies rose 19.3 percent in the quarter, helped by higher prescription volumes from the Rite Aid stores. (Reporting by Manas Mishra in Bengaluru; Editing by Maju Samuel)