Il Nuovo Postiglione - U2 performs surprise 50th anniversary gigs in Dublin

The legendary musicians performed at their old stomping grounds, the Mount Temple Comprehensive School, for an audience of hundreds of students and staff.

Fans later gathered in central Dublin as rumours swirled of a surprise gig at the famous Bewley's Oriental Cafe, with more than 1,000 people packing into one of the city's main thoroughfares, singing "Happy Birthday U2".

The crowd burst into cheers as the band appeared on the balcony of the cafe, playing an hour-long setlist which opened with 1980s hit "I Will Follow" and included classics like "With or Without You" and "Out of Control".

They also played their new single "Silencio", part of an upcoming album, Carnaval de Luz, announced ahead of the landmark anniversary.

The album, which is set to be released on November 13, includes a track featuring a duet between U2 frontman Bono and country music icon Dolly Parton, who died last month.

The band said the song, "Torn" -- which was co-written by Parton, U2 and singer Johnny McDaid -- was the American singer's "last recorded vocal performance".

Kathrin Schanz, 50, who called herself a "lifelong U2 fan" had travelled from Germany to be in the Irish capital for the anniversary. She told AFP it "amazing to be here".

"It was one of their most special concerts ever," Schanz said of the Dublin city centre performance.

U2's Larry Mullen is said to have pinned a handwritten note stating "drummer seeks musicians to form band" on his school noticeboard five decades ago.

The bandmates had their first rehearsal on September 25, 1976, releasing their debut album four years later before taking the world of rock music by storm in the 80s and 90s.

Bono opened the school gig by asking: "We've escaped from the lab. How's the experiment going for you?"

S.Maiolo--INP