Prince is planning a European tour featuring just his voice and piano, with the 57-year-old pop virtuoso saying he wanted a new challenge, reports said Monday.

Prince -- who rarely makes traditional, straightforward announcements on touring -- apparently broke the news by inviting a small group of music writers from European newspapers to his Paisley Park estate in Minnesota.

The Purple One posted a picture on Instagram showing him playing a keyboard for a small group with the caption, "European press," as well as videos of him practicing, although a representative did not immediately return a request for comment.

Spain's El Pais, in an article Monday datelined Minnesota, said Prince would play in 12 countries starting on November 21 in Vienna and finishing on December 22 in Brussels.

Explaining why he wanted to do the tour, Prince was quoted in Spanish as saying: "For starters, it's a challenge."

"I don't want to get bad reviews, but at the same time I don't want to go back to what I feel safe doing because I've done it for 30 years," he was quoted as saying.

"With the piano it's more naked, more pure. You see exactly what you get."

The tour -- entitled "Prince Spotlight: Piano and a Microphone" -- will include four dates each in Britain and Sweden, El Pais said.

He will also perform in Denmark, France, Germany, Italy, The Netherlands, Norway, Spain and Switzerland, it said.

The tour is believed to be the first since Prince's rise to stardom in which he is performing with such stripped-down instrumentation.

Prince is best known for his skill on the guitar and his falsetto voice, along with his dance moves. He has played recent tours with a backup band that includes the all-female group 3rdEyeGirl.

Prince in recent years has preferred to announce concerts with only a few hours advance notice and has sometimes played two shows in one night.