5 Seconds of Summer have expressed their shock at seeing one of their new songs reach No.1 on the US iTunes chart.

The band recently made available the track 'Good Girls' from their upcoming self-titled album on the music downloading service.

The song can be downloaded with pre-orders of the album in the US, Canada and Mexico and today (May 28) it is still No.1 on iTunes.

Speaking on Twitter, 5 Seconds of Summer said that they didn't expect the song to hit the top spot.

They proclaimed: "Actually can not believe "good girls" is number one on American iTunes chart, so epic WE LOVE YOU X."

The band's self-titled debut album meanwhile is due to be released in the States on July 22, although UK fans will get hold of the record on June 30.

Listen to 'Good Girls' below: