Several hundred activists headed by Sergei Udaltsov of the Left Front group rallied in central Moscow Saturday to protest what they said was the Kremlin’s stifling of democracy, as well as corruption and rising prices.Authorities limited the rally to a central square, and riot police started detentions after the protesters moved to the presidential administration building.Moscow police spokeswoman Yelena Perfilova told the Ekho Moskvy radio that Udaltsov and 13 protesters were detained.Popular support for opposition groups is minimal in Russia. Their activities have been thwarted as authorities ban their rallies and police regularly break up their gatherings.