Singer Rihanna performs during the "Rock in Rio" music festival in near Madrid in 2010. - Reuters File Photo

RIO DE JANEIRO: Rock in Rio may be more than a quarter-century old, but the mega-music festival is showing few signs of age with some 600,000 tickets for this year’s incarnation selling out in four days.

The concert series is returning to the Brazilian city of its birth for the first time since 2001, with six shows set for late September and early October – and another event in 2013.

“The pace of sales surprised us,” Roberta Medina, vice president of the festival, said in a statement late Tuesday.

“Fortunately, today we have a different reality in the country, with a strong city that allows us to transform Rock in Rio into a biannual event. Fans can expect that in 2013 there is a new edition of the festival here.”

Sales began on Saturday, with tickets going for 117 dollars for each day of the show. Some 90,000 tickets were snapped up online in the first 10 hours.

The festival will take place September 23-25 and September 30 to October 2, and is set to feature more than 150 international artists and Brazilian stars.

Among the acts taking the stage this year: Katy Perry, Jay-Z, Metallica, Coldplay, Rihanna, Elton John, the Red Hot Chili Peppers, Motorhead, Slipknot, Lenny Kravitz, Shakira, Mana, Evanescence, System of a Down and Guns N’ Roses.

The series’ first event was held in Rio over 10 days in January 1985, and by drawing 1.4 million people it is believed to be the largest rock festival in the world.

The next editions were in 1991 and 2001, before the series ventured overseas, with several Rock in Rio concerts held in Lisbon and Madrid.