Madonna celebrates daughter Mercy James' birthday onstage in Miami

Madonna gave her daughter Mercy James a 10th birthday to remember on Saturday (23Jan16) by inviting her girl to join the superstar onstage in Miami, Florida.

The Vogue singer interrupted her Rebel Heart tour stop at the American Airlines Arena to introduce fans to the birthday girl, before serenading young Mercy and presenting the beaming child with a cupcake and candle.

Madonna shared a photo of the proud moment on Instagram after the show and captioned it, "Make a Wish Mercy James".

The pop star, who adopted Mercy from Malawi in 2009, had previously celebrated her youngest kid's age milestone by posting a photo of mother-and-daughter on social media.

"Happy Birthday to my Beautiful Mercy James!" she wrote beside the image.

The celebrations proved to be a welcome distraction for the mother of four as she continues to battle her ex-husband Guy Ritchie over custody of their teenage son Rocco, who is seeking to stay with his director dad in the U.K. instead of return to the New York home he shares with his mother and siblings.

Madonna took some time to thank devotees for their continued support amid her personal troubles after receiving a sweet letter from superfans on Saturday.

Part of the note, which she shared with her Instagram followers, read: "We're crying with you, but we know you will get through this as you always do... We love you, forever."

In the accompanying caption, Madonna replied, "Thanks soooooo (sic) much for this! It means a lot to me! One word of kindness, it can save me."