Justin Bieber has cancelled one of two shows in Portugal this week due to logistical problems, according to Bieber's manager.

Canadian pop star Bieber was expected to perform at the Pavilhao Atlantico in Lisbon on 11 and 12 March. He will be performing on 11 March but the second show has been cancelled due to "unforeseen circumstances".

Justin Bieber
Justin Bieber performs in a concert at the Manchester Arena in Manchester

Details are scarce but the Toronto Sun reported saying the show was cancelled due to slow ticket sales. Bieber's manager, Scooter Braun, refuted the reports, telling Gossip Cop both shows in Lisbon were sold out but the teenage singer had to cancel the second leg of the Portugal tour due to problems with the unions.

One reason for the cancellation might be the 19-year-old singer's health problems. On 7 March, while performing at the O2 Arena, Bieber collapsed on stage with breathing problems. He managed to complete his performance, with a 20-minute break for oxygen, and was later taken to the hospital for a check-up but if medical concerns are the reason for the cancellation, then it stands to reason both shows would have been cancelled and not just the second.

A statement on the Web site of the Lisbon venue states: "Due to unforeseen circumstances, Justin Bieber was forced to cancel the second performance in Portugal, 12 March. The Canadian singer is eager to play for the Portuguese fans on 11 March. Holders of tickets valid for March 12 should contact the respective place of purchase to receive a refund within 30 days of the date of the scheduled concert, which ends 11 April."

Justin Bieber
Canadian pop star Justin Bieber is held back by a member of his security team as he confronts a photographer outside his hotel in central London in this still image taken from video

Bieber has endured a torrid week, following a confrontation with a British tabloid photographer and his "worst birthday" comments. In addition, Bieber has also had to deal with irate fans after he turned two hours late for the O2 Arena concert. The Daily Mail reported he threw a "massive tantrum" before the show, with sources saying he sat in his dressing room playing video games before the show.