(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.
San Lorenzo won a game of controversial refereeing decisions.
Federico Dominguez put Gimnasia ahead after half an hour by converting a hotly-disputed penalty awarded for hand ball.
The hosts were on the wrong end of another controversial decision when Jorge San Esteban was sent off in the 48th minute for elbowing.
San Lorenzo equalised with a Carlos Kletnicki own goal on the hour before Bernardo Romeo scored an 83rd-minute winner.
German Denis scored twice in the first half to set Independiente on their way to a 3-0 win over Newell's Old Boys in their last game under interim coach Miguel Santoro.
Uruguayan Guillermo Rodriguez added the third in the 45th minute as Independiente went sixth, four points behind the leading trio.
Santoro will make way for Claudio Borghi, who will become in the latest in a long line of coaches bidding to resurrect the once-mighty Red Devils.
Independiente, South American champions a record seven times, have slumped into mid-table mediocrity in the last few years.
(Writing by Brian Homewood in Rio de Janeiro; Editing by Ed Osmond)