A painting depicting politicians Vladimir Putin and Dmitry Medvedev in women's underwear was one of the items Russian authorities confiscated Monday upon raiding a newly-opened St. Petersburg art gallery that had shown solidarity with Russia's gay-rights movement.

The off-beat gallery, known as the Museum of Authority, opened on August 15 with an inaugural exhibit called "The Rulers" that featured paintings by artist Konstantin Altunin of public figures such as President Barack Obama, former Libyan leader Moammar...