Justin Bieber's mother described him as a ''blessing'' as she wished him a happy birthday.

The pop star turned 21 on Sunday (01.03.15) and his mum Pattie Mallette took to Twitter to share a public message of congratulations to her son.

She tweeted: ''Happy 21st Birthday @justinbieber I can't believe it. #Happy21stJB I can hardly believe any of it! What a blessing you are. #LoveMom (sic)''

Pattie also admitted she could scarcely believe her boy was turning 21.

She wrote: ''I can't believe I gave birth 21 years ago. #smh I barely feel a day older than 21 myself!! @justinbieber I can't imagine life without you. (sic)''

Pattie, 38, gave birth to Justin when she was just 17 and split from his father Jeremy when she was 18. Although they separated, both Pattie and Jeremy maintained a friendly relationship and Justin's dad remained in his life.

Justin celebrated his landmark birthday with a party on a private Caribbean Island close to Grenada.

He was joined by a host of pals including rumoured love interests Hailey Baldwin and Yovanna Ventura, and childhood friend Ryan Butler.

The festivities began late on Saturday evening (28.02.15) and continued into Sunday, with the birthday boy appearing to be having a good time as videos and photos posted on social media showed him dancing shirtless to 50 Cent's 'In Da Club' while clutching a large bottle of champagne. Another picture depicted Justin cuddling a brunette beauty.