Police in St Petersburg have seized some 100,000 copies of a pamphlet deeply critical of Russian PM Vladimir Putin, opposition activists say.
The pamphlets were confiscated on the eve of a major business conference in the city which was opened by President Dmitry Medvedev.
Reports say several activists who tried to distribute the brochures were held.
Police said they acted because the shipment of pamphlets did not have the correct documentation, local media say.
But opposition leader Boris Nemtsov, one of the authors, said the police had orders to prevent the distribution of the pamphlets to people attending the St Petersburg International Economic Forum.
The brochure gives a highly critical account of Mr Putin's 10 years in power: first as president and now as prime minister.
One of the main conclusions is that corruption in the country has now reached what it calls a catastrophic scale - not the kind of message the authorities would want the movers and shakers of the global economoy to be reading during the gathering in St Petersburg, the BBC's Richard Galpin in Moscow says.