Katy Perry will debut songs from her new album in London next month.

The 28-year-old singer announced yesterday (20.08.13) she'll be jetting to London to close the city's iTunes festival on September 30, where she'll be raising the roof with a full set, expected to include new track 'Roar' and preview other songs from her forthcoming third album 'Prism'.

She tweeted: ''PUMPED to announce I will be closing the month-long @iTunesFestival on 9/30 with my friends @IGGYAZALEA & @iconapop opening! (sic).''

The official Twitter account for iTunes later posted: ''We saved the fireworks for last. The #iTunesFestival proudly welcomes @katyperry on 30 September (sic).''

The brunette beauty has joined a star-studded line-up for the festival, alongside Robin Thicke, Justin Timberlake, John Legend, Kendrick Lamar and Kings Of Leon, as well as chart rival Lady GaGa.

Katy is currently on course to outsell the outrageous Gaga with her new 'Roar' - the first single from 'Prism' - by double the amount of the 27-year-old singer's new song, 'Applause', as the pair battle it out in the US charts.

According to Billboard, Katy will shift between 525,000 and 550,000 copies of her comeback song, while Gaga is set to sell 200,000 to 225,000 when the charts are counted later this week.

'Applause' debuted at number five in the UK charts last Sunday (18.08.13), while 'Roar' is expected to enter the UK rundown this weekend.