Russia protests: Activist Navalny detained, wife tweets

Russian opposition leader Alexey Navalny has been reportedly detained by authorities in Russia as protesters -- engaged in a day of nationwide demonstrations -- braced for clashes in Moscow on Monday.

Navalny's wife, Yulia, reported the news of his detention at his home in the Russian capital on his official Twitter feed. She also posted a picture on his twitter feed which shows police officers at the scene.

Meanwhile Navalny's YouTube channel, which had been broadcasting live to more than 50,000 people as protests across Russia got underway, lost light and sound.

Hours earlier, authorities declared that a planned rally in the Russian capital was illegal.

"We warn that any attempts to hold an illegal event on the Tverskaya Street, Moscow is a direct violation of the law," the Prosecutor General said in a statement.

"Law enforcement agencies will be forced to take all necessary measures to stop provocations, mass unrest or any actions leading to a violation of public security, creating conditions for threatening the life and health of citizens."

The Moscow rally is one of nearly 200 planned for towns and cities to mark the Russia Day public holiday. Protests in the far east of the country were already underway and campaigners had hoped more than 10,000 people would attend in St. Petersburg and in Moscow.

Navalny -- -- who plans to run against Vladamir Putin in next year's presidential election -- said earlier they would go ahead regardless of whether the government allowed them or not.

The 41-year-old has been mobilizing support on social networks, and hopes the rallies will rattle the Kremlin, as those held earlier this year did.