5 Seconds of Summer have expressed gratitude and shock at their rise to fame.

The Australian pop-punk band have become a major force in the music industry since releasing their debut album last year.

The quartet, however, had modest beginnings and they took to Twitter to express their surprise at how far they have come.

Writing on the website on Sunday (February 15), 5 Seconds of Summer said:

"Can't believe we hit 6m followers on this account. That's a sh*tload of awesome people. I still remember when we had 10k."

The band meanwhile are currently working on the follow-up to their self-titled 2014 debut record.

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Watch 5SOS being interviewed below: