Justin Bieber 'in photographer altercation'

Justin Bieber has allegedly threatened to "beat" a photographer.

The singer has been in the UK this week to play a string of shows in London. He has been dogged by controversy after he took to the stage a reported two hours late on Monday, despite many of his awaiting fans needing to be at school the next day.

Yesterday he collapsed backstage after suffering shortness of breath and was taken to hospital, although he has assured fans he is fine.

According to TMZ the star was leaving his hotel in the British capital today when he became upset with a waiting paparazzi.

Justin reportedly came into contract with the man as he scurried through a scrum of photographers while trying to get to his SUV.

The paparazzi was heard complaining about the 19-year-old, causing the teenager to lose his cool.

As his minder pushed him back into the vehicle, Justin apparently yelled: "What the f**k you say? I'll f**king beat the f**k out of you."

The singer reportedly lashed out at the unidentified man in an effort to hit him, but his bodyguards stopped the blow from connecting.

Justin was eventually forced back into the car, which drove away.

The teenager quickly took to his Twitter page to update fans on the incident.

"Ahhhhh! Rough morning. Trying to feel better for this show tonight but let the paps get the best of me...," he wrote.

"Sometimes when people r shoving cameras in your face all day and yelling the worst thing possible at u...well I'm human. Rough week. Not gonna let them get the best of me again. Gonna get focused on this show tonight. Adrenaline is high now. Gonna put it on the stage. Only way someone can break u is if u let them (sic)."

Despite his illness last night, Justin will be performing for fans at the O2 Arena in London again tonight.