BERLIN -- Irish rockers U2 returned to Berlin for a free mini-concert Thursday in front of the Brandenburg Gate, playing its classic singles and a duet with Jay-Z even as the show was obscured from outside public view by a nearly 6-1/2-foot-high metal barrier.

Bono greeted the crowd with the German words "Berlin, Du bist wunderbar!" (Berlin, you are wonderful!) and the band played a 30-minute, six-song set that featured "Sunday, Bloody Sunday," "One" and "Beautiful Day."

Rapper Jay-Z appeared as a surprise guest and performed Bob Marley's "Get Up, Stand Up" with Bono.

The show, which was free to 10,000 ticket holders who snapped up the tickets online last week in just three hours, drew some controversy because of the barrier surrounding the gig.

Both Berliners and tourists alike saw the irony in building a wall around a concert dedicated to the wall that already has come down.

"It's completely ridiculous that they are blocking the view," said Louis-Pierre Boily, 23, who came to Berlin even though he failed to get U2 tickets. "I thought it's a free show, but MTV probably wants people to watch it on TV to get their ratings up."

Boily, from Quebec City, was among several hundred people who gathered earlier in the day against the new fence, which was draped with a white tarp that blocked the view of the stage from the street. Some fans already were trying to tear down the tarp before the concert.

The music network MTV, which organized the concert, said it worked with the local promoter, the city and Berlin police to install a temporary fence "around the site to ensure the safety and security of the attendees at the event as well as residents and businesses in the area."

U2's publicist RMP refused comment about the barrier.