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. Multiple YouTube channels broadcast the event live.

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

The watchdog, Roskomnadzor, said some entities had been buying advertising tools from YouTube, such as push notifications, in order to spread information about illegal mass protests, including those aimed at disrupting elections.

It said Russia would consider a failure by Google to respond to the request as "interference in its sovereign affairs" and "hostile influence (over) and obstruction of democratic elections in Russia."

If the company does not take measures to prevent events from being promoted on its platforms, Russia reserves the right to respond accordingly, Roscomnadzor said, without giving details.

Over the past five years, Russia has introduced tougher laws requiring search engines to delete some search results, messaging services to share encryption keys with security services, and social networks to store Russian users' personal data on servers within the country.