UPDATE 1-Soccer-Boca beat River for first time in three years

(updates with San Lorenzo result, Riquelme quotes)

BUENOS AIRES, May 4 (Reuters) - Boca Juniors beat arch-rivals River Plate 1-0 on Sunday, the first time in three years they have won the meeting of Argentina's two most popular clubs.

Sebastian Battaglia scored the only goal to throw the Apertura championship wide open, moving Boca one point behind leading trio River, Estudiantes and San Lorenzo with six matches to play.

Estudiantes, who top the table on goals scored from River, lost 2-1 at Argentinos Juniors on Saturday while San Lorenzo won 2-1 at Gimnasia-La Plata. The three teams have 27 points from 13 games.

Boca dominated the early stages at the Bombonera and Rodrigo Palacio wasted an excellent chance when he broke clear but shot straight at Juan Carrizo.

The hosts went ahead in the 14th minute when midfielder Battaglia shook off his marker to meet Juan Roman Riquelme's corner with a powerful header.

"Boca deserved to win because River did nothing," said Riquelme.

Boca previously beat River in May 2005 and the five meetings since then have produced three draws and two wins for River.

Gabriel Hauche and Alejandro Delorte gave Argentinos a 2-0 lead against Estudiantes and Mauricio Carrasco pulled one back for Roberto Sensini's team.