Millie Bobby Brown has surprised fans by singing a Katy Perry tune at Argentina Comic Con.

The actress rose to fame in 2016 for her portrayal of Jane 'Eleven' Ives in Netflix drama series Stranger Things, and has since landed a modeling debut in Calvin Klein's By Appointment campaign.

And during an appearance at the Argentina Comic Con event in Buenos Aires on Friday (26May17), Millie unveiled her singing talent.

Video footage posted on social media shows the 13-year-old asking the crowd, "Ready everyone?"

She then launches into a version of hymn Ave Maria before proceeding to sing a rendition of Katy's 2010 song Firework, garnering a huge round of applause from the packed audience.

During her time onstage at the event, Millie also spoke about her connection to character Eleven, who has psychokinetic abilities and a limited vocabulary.

"She is powerful, iconic, a woman and a hero," she shared. "I loved it (the look of Eleven) and knew right away that I would love the complete look to the character."

The starlet also took to Instagram following her performance, sharing a photo of her standing on the stage holding the Argentinian flag in front of the crowd. Millie, who born in Marbella, Spain and now resides in London and Los Angeles, chose to caption the snap in Spanish.

"Argentina, what can I say?" the message translates as. "You are such beautiful and passionate fans and it has been a privilege to meet you guys! I love you to the moon and beyond!"