GREEN DAY frontman Billie Joe Armstrong was spotted in Glasgow ahead of his gig in the city.

The band behind hits such as Basket Case and American Idiot are in town to perform in the Hella Mega Tour at Bellahouston Park. 

But before taking his turn on the stage, lead singer Billie Joe headed to a much smaller but much-loved venue to watch a gig.

The 50-year-old popped into King Tut's Wah Wah Hut to see a performance by US singer-songwriter Jesse Malin.

Photos shared on Twitter show Billie Joe leaving the venue after the gig.

A fan wrote that it "was surreal to have Billie Joe Armstrong brush past me in such a tiny (but iconic) venue".

Green Day will perform alongside fellow American rockers Weezer and Fall Out Boy tonight.