Bieber's teenage fans, known as 'Beliebers,' went wild when the 18-year-old singer took to the stage on Monday with a troupe of dancers, an impressive lights show and his signature bright sneakers.

Mexico City authorities estimated 210,000 people thronged the main square to see Bieber perform hits such as "Baby", "Never Say Never" and his latest single "Boyfriend."

Some die-hard "Beliebers" had camped out for days in central Mexico City to ensure prime position at the mega concert. Mexican authorities enforced tight security, looking to avoid the kind of stampede that injured more than 40 young Bieber fans at a free show last month in Oslo.

Bieber, who was discovered on YouTube in 2008, has adopted a more edgy image and sound on his new album than the catchy pop tunes that first made him a teen idol.

But the singer told a news conference ahead of his Mexico City show that "being 18, I feel like I do have a responsibility to be a good role model."

"I'm not perfect but at the end of the day I always want to send a message .... Everybody, no matter being young or old, can always use a positive message; that's why I named my album 'Believe'," he said.

Mexico City is one of only seven cities around the world that Bieber chose to showcase tracks from his highly anticipated album, out June 19, following stops in Oslo, Paris and London.

(Reporting by Reuters TV, writing by Piya Sinha-Roy; Editing by Jill Serjeant and Richard Chang)

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