Gwen Stefani

Gwen Stefani

U2 stunned fans on Tuesday (09Sep14) by releasing their highly-anticipated new album for free after performing at Apple's iPhone 6 unveiling event in California.

The Beautiful Day hitmakers closed the technology conference by treating attendees, including celebrity audience members Gwen Stefani and British actor Stephen Fry, to a special set, before Apple boss Tim Cook announced U2's new project, Songs of Innocence, would be made available for free to iTunes users that afternoon.

The album will go on sale to the general public next month (Oct14).

The surprise release comes six months after a U2 spokesperson dismissed rumours suggesting the band had delayed plans to unveil the follow-up to 2009's No Line on the Horizon until next year (15).