ST PETERSBURG, Feb. 17 (Reuters) - More than 400 people have been detained at events across 32 Russian cities since the death of Alexei Navalny, President Vladimir Putin's most formidable opponent, according to rights group OVD-Info, as Russians continued to gather and lay flowers.

It has been the largest wave of arrests at political events in Russia since Sept. 2022, when more than 1,300 were arrested at demonstrations against a "partial mobilisation" of reservists for Putin's military campaign in Ukraine.

Navalny, a 47-year-old former lawyer, fell unconscious and died on Friday after a walk at the "Polar Wolf" Arctic penal colony where he was serving a three-decade sentence, the prison service said.

OVD-Info, which reports on freedom of assembly in Russia, said the largest numbers of arrests occurred in St Petersburg and Moscow, where Navalny's support had traditionally been strong. As of 2000 GMT on Saturday, more than 200 people were detained in St. Petersburg.

But there was no mention of the events on Russian state news agencies, which are under full Kremlin control. There was also no stories about the hundreds of people across Russia who have continued to defy authorities to lay flowers at impromptu Navalny memorials.

The death of Navalny robs the disparate Russian opposition of its most prominent leader as Putin prepares for the March presidential election - a rubber-stamp vote set to keep the former KGB spy in power until at least 2030.

Footage filmed by Reuters on Saturday in St Petersburg showed dozens gathering by a monument to the victims of repression. Protesters laid flowers and candles, while some sang hymns and others hugged each other, shedding tears.

"I felt very sorry for him and for our country," said an 83-year-old woman attending the vigil who declined to give her name. "I'm scared."

A Reuters reporter at the scene said some 30 people were arrested shortly after the singing finished.

Photo from Reuters