The Toxic hitmaker has been headlining her Britney: Piece of Me concerts at Planet Hollywood Resort and Casino since December, 2013, and now that she has extended her stay until 2017, she's personally inviting some of her biggest fans to see the concert for free.

One fan named Alycia, who goes by the online moniker of 'Fit Like Britney' and uses her account to document her weight loss journey, shared a snap of the note alongside the caption: "Today something beyond unexpected and beyond my wildest dreams happened. I received a handwritten card from Britney herself. The moment I opened it and saw my name, I immediately recognized the handwriting and burst into tears."

In the card, Britney wrote, "Alycia, Your hard work and dedication are so inspiring - you look amazing! You are a beautiful person inside and out. Would love for you to reward yourself and come to one of my shows in Vegas in 2016! Let me know what day, and I'll make sure you get a pair of tickets."

Another fan called Cody took to to share his note from the pop star and wrote, "I JUST GOT A LETTER FROM BRITNEY F**KING SPEARS. THANK YOU SO MUCH BRITNEY. I LOVE YOU."

Britney wrote to him, "Cody, I wanted to send you a little note and say thank you for all your support over the years! You always make me and the people around you smile. That is such a gift! You know what would really make me smile? Seeing you in Vegas next year! You let me know what should (sic) and I'll save you 2 tickets!"

Several other fans have also posted their personalised notes received from Britney on social media.