In the run-up to the Sept 8 elections for Moscow's regional Parliament, or Duma, the Russian authorities have been cracking down on public protesters, with more than 2,000 arrested during two incidents in late July and early this month.

The protests were triggered by the mass "barring" of opposition candidates who wanted to take part in the elections. The elections are seen as a testing ground for more important ones to come - in 2021, when the Russian Parliament is elected and in 2024, when a new president is due to assume office.