Justin Bieber has cancelled a concert in Lisbon, Portugal, on Tuesday (12.03.13) due to ''unforeseen circumstances''.

The 19-year-old pop superstar endured a tough week when his 'Believe Tour' hit London last week, receiving heavy criticism for turning up late to his show last Monday (04.03.13) and he then needed oxygen backstage on Thursday (07.03.13) after complaining of breathlessness.

Justin has decided to pull the plug on his scheduled gig at the Pavilhao Atlantico indoor arena but will still perform at the venue in tonight (11.03.13).

A statement posted on the arena's website reads: ''Due to unforeseen circumstances, Justin Bieber was forced to cancel the second performance in Portugal, March 12. The Canadian singer is eager to play for the Portuguese fans on March 11.''

Local reports have suggested the show has been scrapped due to poor ticket sales. All ticketholders have been offered full refunds.

Justin's disastrous stop in the UK culminated with an altercation with a paparazzi photographer on Friday (08.03.13) during which the 19-year-old singer threatened to ''beat the f**k'' out of the snapper.

The 'Never Say Never' hitmaker's 'Believe Tour' is due to reach Madrid, Spain, on Thursday (14.03.13).