Lady GaGa has cancelled two shows after being struck down with bronchitis.

The 28-year-old singer was forced to pull out of a gig in Seattle last night (28.05.14) and has cancelled a further show in Vancouver on the American leg of her 'artRAVE Tour' due to the illness.

She took to Twitter today (29.05.14) to apologise to fans for the inconvenience, writing: ''I'm devastated I'm unable to perform this week. Ursula took my mermaid voice. I've come down with horrible Bronchitis (sic),'' making reference to the fictional sea witch from 'The Little Mermaid', who uses Ariel's voice to cast a spell in the popular Disney movie.

Gaga also insisted she would reschedule the cancelled shows so fans could see her live, posting: ''My deepest apologies to Seattle and Vancouver, we'll reschedule those shows & be back to make it up to you. I <3 monsters. #sadgaga (sic).''

Fans were quick to wish her well and she posted: ''Thanks for understanding,'' adding, ''Im so sorry. I'm holding stuffies and wearing seashell bra. With tissues and wigs. (sic)''

Meanwhile, the star is set to head to the UK in October and has added a number of extra arena shows in Birmingham, Sheffield, Newcastle and Glasgow after a massive demand for tickets.

She has also added a third date at London's O2 Arena to her UK and Ireland tour schedule, after the first two nights sold out just minutes after tickets going on sale.