Madonna and Lady Gaga could face prosecution in Russia for violating the terms of their visa to enter the country, officials there say. The singers were each allowed in to Russia on "cultural exchange" visas, The Guardian reports, which don't permit commercial activity like performing concerts.

Russian authorities say Madonna, who performed there in August 2012, and Gaga, who played there in December, arrived on cultural-exchange visas, which "do not grant their bearers the right to engage in any commercial activity." Prosecutors are considering their options in asking the Ministry of Foreign Affairs or Federal Migration Service to press charges against Madonna and Gaga.

The office of Russia's prosecutor general began an investigation after a complaint from Vitaly Milonov, a St. Petersburg legislator who authored the city's controversial anti-gay legislation, which Madonna spoke out against during a performance there last August. Milonov later accused her of performing without the proper paperwork. Lady Gaga is also a vocal ally for LGBT causes.

Russian promoters are now on edge regarding future tours from foreign artists and tourism around the upcoming Winter Olympics in Sochi next year. "Not one artist, circus or exhibition will come here if the prosecutor's office fines someone now," Yevgeny Finkelstein, head of the St. Petersburg-based PMI media holding, told RIA Novosti.

Lady Gaga has responded to the Russian government's claim last week that the pop star could face prosecution for violating the terms of her visa by performing in the country. In a Facebook post expressing support for the Russian LGBTcommunity, Gaga concluded with a pointed question: "Why didn't you arrest me when you had the chance, Russia? Because you didn't want to answer to the world?"

Russian authorities have said that Gaga and Madonna were granted cultural exchange visas that do not allow commercial activity such as concert performances. But the governmentbegan investigating the singers following a complaint from a St. Petersburg legislator who also authored controversial anti-gay legislation. Both Gaga and Madonna have advocated on behalf of gay Russians, with Gaga reiterating her support on Facebook.

"Sending bravery to LGBTs in Russia," she wrote. "The rise in government abuse is archaic. Hosing teenagers with pepper spray? Beatings? Mother Russia? The Russian government is criminal. Oppression will be met with revolution. Russian LGBTs you are not alone. We will fight for your freedom."