Justin Bieber has paid tribute to his ex-GF Selena Gomez on Instagram - describing her as the "most elegant princess in the world".

The pop star, who celebrated his 20th birthday at the weekend, shared a snap by a professional photographer of Sel-Go on the red carpet for the Vanity Fair Oscars after party.

Wearing a sheer-and-gold floor-length gown, the 21-year-old singer-turned-actress was praised by many critics for her choice on Hollywood's big night.

Selena didn't respond to Biebs' compliment, but did share a snap of herself and Spring Breakers co-star Vanessa Hudgens enjoying a cuddle together later in the evening.

She wrote: "@vanessahudgens my only, official party buddy for life ;)"