Selena Gomez is transforming from Disney princess to pop diva with each passing day. 

The 19-year-old took to the stage in Puerto Rico last night in a daring gown worthy of a Las Vegas showgirl.

She wore a blue dress with a plunging neckline, sequinned hotpants and slinky skirt that fluttered around her exposed legs as she danced.

Selena’s blue and purple highlights matched her scene-stealing dress during the opening night of her South American tour.

The former Wizards of Waverly Place star wrote on her Facebook page ahead of the concert: ‘Puerto Rico – 4 hours til show time, so excited to be back such a fun place to kick off my South American Tour it’s like my second home. Love you all.’

The tour will take in Panama City, Mexico City, Santiago, Rio de Janeiro, Sao Paolo and Buenos Aires, among others.

The 5ft 5 star was spotted making her way through the airport in Puerto Rico earlier in the day after flying in from Los Angeles.

Also jet-setting yesterday was her boyfriend Justin Bieber, who was at LAX in a pair of crazy eye-grabbing socks.

There was no night off for Selena before she jetted out on tour. Over the weekend she hosted her second annual concert to benefit UNICEF at the House of Blues on the Sunset Strip.

Selena has been an ambassador for the charity for two years, and has even travelled to Ghana and Chile to bring awareness about certain issues.

In 2011 she helped launch Celebrity Tap, which raised money to help UNICEF provide water and sanitation programs in Togo, the Central African Republic and Vietnam.

Selena, along with boyfriend Justin and David Beckham, raised $200,000 for the charity.