Russian opposition leader Alexei Navalny held ahead of rally
Police in Russia have detained opposition leader Alexei Navalny ahead of a rally in a major city.
Mr Navalny posted a video on his Instagram account of what he said were officers outside his home asking him to come to a police station.
He tweeted from the station later, saying he had not been told why he had been detained.
Mr Navalny had planned to travel to the city of Nizhny Novgorod where he was to lead a rally later on Friday.
After he announced his presidential bid last year, Mr Navalny, a top Kremlin foe and arguably Russia's most popular opposition politician, inspired a grassroots campaign in Russian regions to support his nomination.
The Tass news agency on Friday quoted police as saying Mr Navalny was detained because of his calls for unsanctioned rallies.
The rally in Nizhny Novgorod, however, had received City Hall approval.
Mr Navalny's associates, in the meantime, reported that police seized their equipment, which was already installed at a city square ahead of the rally.
"The Kremlin views my meetings with voters as a huge threat and even an insult," Mr Navalny tweeted.
"They were saying for so long that opposition has no support in the regions, and it now pains them to even look at our rallies."
He recorded and posted online a video from the police station, calling on his supporters in Nizhny Novgorod to come to the rally even if he does not make it there.
The Kremlin has dismissed Mr Navalny, who has faced repeated jailings and criminal cases, as an urbanite out of touch with people living in Russia's 11 time zones where President Vladimir Putin draws his support from.
That began to change earlier this year when Mr Navalny opened campaign offices in 80 cities and towns, most of which had not seen a political life for decades, attracting thousands of supporters.