Christmas has come early for Madonna fans, although for the singer, the celebration is bittersweet.

The 56-year-old Queen of Pop released six out of 19 tracks from her upcoming 13th studio album, Rebel Heart, after unfinished demos of several of them were leaked online this week, in a move that the singer called "artistic rape" and "a form of terrorism."

The songs were made available for purchase on iTunes on Saturday, five days before Christmas. One of them, titled "Bitch, I'm Madonna," features hip-hip star Nicki Minaj.

More tracks will be released on Feb. 9, according to a statement posted on Madonna's website.

"The decision to release the songs much earlier than anticipated was due to the leaking of several work-in-progress demos earlier this week," it said.

"I was hoping to release my new single 'Living For Love' on Valentine's Day with the rest of the album coming in the spring," the singer was quoted as saying. "I would prefer my fans to hear completed versions of some of the songs instead of the incomplete tracks that are circulating. Please consider these six songs as an early Christmas gift."

Her manager, Guy Oseary, had put out a plea to fans on Twitter in late November, saying, "I would be grateful to any @madonna fans that can assist us in finding those responsible for the leak.. We appreciate your help.."

It is unclear if he was referring specifically to the leaked album tracks.

The released tracks are:

1. "Living for Love"

2. "Devil Pray"

3. "Ghosttown"

4. "Unapologetic Bitch"

5. "Illuminati"

6. "Bitch, I'm Madonna (featuring Nicki Minaj)

Rebel Heart contains explicit content and is set for release in its entirety on March 10, 2015.

Listen to "Living for Love," an upbeat dance track, below.