Russia's state communications watchdog said on Sunday it had asked Google to stop advertising "illegal mass events" on its YouTube video platform.

Tens of thousands of Russians staged what observers called the country's biggest political protest for eight years on Saturday, defying a crackdown to demand free elections to Moscow's city legislature.

The watchdog, Roscomnadzor, said Russia would consider it interference in its sovereign affairs and a hostile influence should Google fail to respond to the request.