Spy widow joins anti-Russia protest
Russian billionaire Boris Berezovsky and the widow of former spy Alexander Litvinenko have joined a protest outside the Russian embassy.
About 30 people waving placards attended the anti-Kremlin rally in central London which, unlike similar events in Moscow and St Petersburg, passed off peacefully.
Opponents of prime minister Vladimir Putin and rights activists have been gathering on the 31st of each month to honour the 31st article of the Russian Constitution, which guarantees the right of assembly.
In Moscow, opposition leader Boris Nemtsov was detained and police officers hauled away protesters who were chanting "Down with the police state!" and "Russia without Putin!"
Russian police told the Interfax news agency that more than 60 people were detained while another 70 protesters were held at a rally in St Petersburg.
Mr Putin has said police will keep breaking up the protests unless the dissidents obtain official permission - which they are routinely denied.
"You will be beaten upside the head with a truncheon. And that's it," he said.
In London, Mr Berezovsky and Marina Litvinenko were accompanied by burly security guards wearing earpieces.