Minutes after protesters unfurled anti-Kremlin banners and chanted "Down with KGB power" and "Russia without Putin," a dozen young men jumped out of cars and started to beat them with fists and metal rods. The thugs first attacked elderly marchers who were walking slowly at the back of the crowd of about 50. When Alexey Kazakov, a protest leader, tried to intervene, some of the assailants surrounded him and started punching and kicking.