UPDATE 2-June sales rise at Walgreen, fall at Rite Aid

* Walgreen same-store sales up 3.4 pct

* Rite Aid same-store sales down 0.6 pct

* Rite Aid shares fall 7.1 pct; Walgreen down 1 pct (Adds Rite Aid's sales, details on Walgreen's performance)

CHICAGO, July 2 (Reuters) - Sales rose at Walgreen Co (WAG.N) and fell at smaller rival Rite Aid Corp (RAD.N) in June as shoppers filled more prescriptions but bought less discretionary summer merchandise.

Walgreen, the largest U.S. drugstore chain by revenue, said on Thursday that sales at stores open at least a year rose 3.4 percent in June. They increased 5.8 percent at its pharmacy counters and fell 0.9 percent in the front end of its stores, where it sells merchandise such as candy, cosmetics and household products.

Walgreen said its same-store sales got a boost because there was one more weekday in June 2009 than a year earlier. Customers tend to fill more prescriptions on weekdays than on weekends.

At Rite Aid, the third-largest U.S. drugstore chain, same-store sales fell 0.6 percent in the four weeks ended June 27. They rose 1.4 percent in its pharmacy sections and fell 4.5 percent at the front end.

Rite Aid had warned investors last week that sales of summer merchandise were weak, likely because of the wet and cool weather blanketing much of the country.

The company said sales were more sluggish at the Brooks and Eckerd stores it acquired from Canada's Jean Coutu (PJCa.TO) in 2007 than at its other stores.