Wearing a leather jacket and dancing under the watchful eye of his bodyguard and grinning guitarist, the 18-year-old sang hits like "Baby" and "One Time" to the increasingly frenzied crowd gathered at a street behind the Pantheon monument in the Latin Quarter.

Some of Bieber's fans, who waved messages saying "Thank You Justin" and got into occasional scraps with security guards in front of the building, had waited hours for their idol after being told via Bieber's Twitter feed to "sing with" Justin at the offices of record label Universal in Paris.

"We've been here since 10:30 a.m...We got in a taxi and came straight here after it appeared on Twitter," said 21-year-old student Sonia O'Donnell, accompanied by her friend Sinead Murphy.

Not everyone was as pleased by the noise as the true "Beliebers" were. One glum-looking Parisian living at a neighboring building held a makeshift flag up at his window with the words: "Bieber Go Home".

(Reporting by Lionel Laurent, editing by Paul Casciato)

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