Fifteen years after leaving Smashing Pumpkins, guitarist James Iha has rejoined the alternative rock icons to perform songs from the classic 1993 album "Siamese Dream."

Iha, who last appeared with Smashing Pumpkins in their native Chicago in December 2000, unexpectedly walked onto a Los Angeles stage on Saturday night to play with the band, according to videos posted online by fans.

"Yes, it's James Iha," Billy Corgan, the band's frontman and undisputed leader, told a cheering crowd.

Sporting a blazer, Iha brought back the early Pumpkins' signature fuzzy noise on electric guitar as Corgan sang and strummed an acoustic guitar.

The reunited band played tracks off "Siamese Dream" -- notably the emotionally intense "Disarm" and the more upbeat "Today" -- as well as a cover of the Rolling Stones' "Angie," according to social media posts.

The show was all the more surprising as Corgan is known for disliking talk of reunions and frequently performs concerts solely with new material, saying he does not want to be stuck artistically on selling nostalgia.

But in a recent interview with Rolling Stone magazine, Corgan said he had developed "an open-door policy" for Smashing Pumpkins and felt no need to define who was a member or not.

The band was famous for its internal friction. During the recording of "Siamese Dream," which catapulted the group to fame, the perfectionist Corgan would overdub his own playing to replace the contributions of Iha and bassist D'arcy Wretzky.

The Pumpkins' reunion is still without Wretzky, who has had well-publicized drug problems and has kept a low profile since the band's 2000 breakup.

Drummer Jimmy Chamberlin was fired in 1996 over drug use after keyboardist Jonathan Melvoin died of a heroin overdose while in New York on tour.

But Chamberlin returned to the band after rehab and has joined Corgan in the second incarnation of Smashing Pumpkins that began in 2006.

Chamberlin wrote on Twitter after Saturday's show that it was "pretty cool" to play again with Iha and was "looking forward to doing it again sometime."

Smashing Pumpkins were one of the most influential bands of the 1990s, moving from a grunge sound to incorporate operatic and electronic elements to songs defined by Corgan's dark introspection.

Corgan, 49, in recent years has pursued diverse side projects that have included writing plots for professional wrestling matches and creating an eight-hour electronic interpretation of "Siddhartha," Hermann Hesse's celebrated 1922 novel inspired by the Buddha.