LONDON (AP) — Justin Bieber's week just got worse.
Following a brief hospital stay after fainting backstage, the 19-year-old pop star's preparation for a final concert in London on Friday hit a speed bump.
Bieber got into an altercation with insult-hurling paparazzi, lashing out at a photographer with a stream of expletives as he was restrained by minders.
The singer quickly took to Twitter to address the incident, which was captured by Channel 5 news, and pledged to channel his "adrenaline" into his Friday show.
"Ahhhhh! Rough morning. Trying to feel better for this show tonight but let the paps get the best of me," he posted on the social networking site.
"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."
The scuffle came just hours after Bieber said he was "getting better" after struggling to breathe during the previous night's concert at the O2 arena, and pledged the show would go on as planned.
A spokesman for the O2 Arena said the 19-year-old pop star was treated backstage during Thursday's concert after becoming short of breath, but recovered and finished his set.
Bieber later posted a shirtless photo of himself in a hospital bed, saying he was getting better and listening to Janis Joplin. Before that on Twitter he thanked "everyone pulling me thru tonight."
"Best fans in the world," he wrote. "Figuring out what happened. Thanks for the love."
Video footage from the concert shows Bieber appearing to fade during a performance of his up-tempo hit, "Beauty and a Beat." He slows down, puts a hand to his head then bends over, resting his hands on knees before walking slowly to the back of the stage.
The incident caps a difficult week for Bieber. He was forced to apologize to outraged fans who accused him of taking the stage almost two hours late for his first concert at the O2 on Monday. He insisted he was only 40 minutes late and blamed "technical issues." He took to Twitter to vent his frustrations with the media's portrayal of the incident.
The star's Believe world tour is due to move on to Portugal on Monday, then continue across Europe, the Middle East, South Africa and North America until August.