International pop star Madonna has been accused of failing to acquire a proper work permit to hold two concerts in Russia last August.

The 54-year-old singer took her MDNA tour to the country last summer for shows in Moscow and St. Petersburg, but Russian officials have now suggested the star did not have the proper paperwork for commercial performances.

Madonna caused controversy during her visit by openly backing incarcerated musicians Pussy Riot and promoting gay rights, a move which sparked a lawsuit from conservative activists. The legal action was dismissed by a judge earlier this year.

Now, the Like A Virgin singer is said to have obtained the wrong kind of visa for her visit and concert organizers may now face a hefty fine and could face a ban from Russian authorities.

A statement from Russia's Foreign Ministry reads, "If a foreign national's activity in Russia is aimed at making a profit, including through commercial performances, the said national must receive a work permit from the Federal Migration Service, and therefore must be issued a normal work visa, with the purpose of the visit stated as work for hire."

Foreign Ministry officials were asked to look into Madonna's visa situation by St. Petersburg legislator Vitaly Milonov, who tells Russian newspaper Izvestia, "Those who applied for a visa for Louise Ciccone (Madonna) face a fine of 500,000 rubles ($15,885.00). It has to be determined whether (Madonna) filed the documents herself."

"The question of the legality of Madonna's visit to our country will also come up, and next time it will be a lot more difficult to get a visa."