By Guy Faulconbridge

MOSCOW, Dec 14 (Reuters) - Several dozen people protested on Sunday in the Siberian city of Tomsk against Russia's ban on U.S. children's gaming platform Roblox RBLX.N, a rare show of public dissent as popular irritation over the ban gains some momentum.

In wartime Russia, censorship is extensive: Moscow blocks or restricts social media platforms such as Snapchat, Facebook, Instagram, WhatsApp and YouTube while distributing its own narrative through a network of social media and Russian media.

Russia's communications watchdog Roskomnadzor said on December 3 it had blocked Roblox because it was "rife with inappropriate content that can negatively impact the spiritual and moral development of children".

In Tomsk, 2,900 km (1,800 miles) east of Moscow, several dozen people braved the snow to hold up hand-drawn placards reading "Hands off Roblox" and "Roblox is the victim of the digital Iron Curtain" in Vladimir Vysotsky Park, according to photographs provided by an organiser of the protest.

"Bans and blocks are all you are able to do," read one placard. The photographs showed about 25 people standing in a circle in the snow, holding up placards.

In Russia, the ban on Roblox has triggered a debate over censorship, child safety in relation to technology and even the effectiveness of censorship in a digitalised world where children can bypass many bans in a few clicks.

Many Russians simply circumvent bans by using VPNs (Virtual Private Networks), though some young Russians have questioned the logic of a ban if it can be so easily bypassed while others have questioned why there are so few Russian alternatives to the apps which the state has banned.

Some Russian parents and teachers have said they were concerned Roblox allowed children to access sexual content and communicate with adults.

Roblox, headquartered in San Mateo, California, has been banned by several countries including Iraq and Turkey over concerns about predators exploiting the platform to abuse children.

The company did not immediately respond to a request for comment. When the Russian ban was introduced, Roblox said it has "a deep commitment to safety" and provides "rigorous built-in protections to help keep users safe".

Russian officials say they need censorship to defend against a sophisticated "information war" unleashed by Western powers, and what they cast as decadent Western culture which undermines "traditional" Russian values.

(Reporting by Guy Faulconbridge;Editing by Helen Popper)

((guy.faulconbridge@thomsonreuters.com; Telephone +79856400243;))