Claims that law aimed at blacklisting websites devoted to drugs, suicide and paedophilia is being used as a censorship tool

Russian internet users warned on Monday that a new law aimed at blacklisting websites devoted to drug use, suicide promotion and paedophilia was being used as a tool for censorship after two popular sites were banned.

More than 180 sites have been banned since the law came into effect on 1 November, RIA-Novosti, a state-run news agency, reported. No official public register of the blacklist exists, though the government has opened a portal where users can check to see if specific sites are on it.

Analysts have warned that the vaguely worded law could be manipulated to crack down on the Russian internet, the one media platform untouched by the Kremlin's heavy hand.

Two websites crucial to Russia's Internet subculture – a Russian version of anonymous imageboard and discussion site 4chan, and Lurkmore, a humorous Wikipedia-style site – said on Monday that they had both been added to the blacklist. Popular among Russia's tech and hacking communities, both sites managed to switch to different IP addresses and remain running.

Lurkmore, with pages designed to look like Wikipedia, includes an entry on Vladimir Putin that collects insulting video and images of the leader, and describes him in terms such as "botox president", a reference to rumours of plastic surgery.

Dmitry Homak, one of the site's co-founders, said Lurkmore was only alerted to the ban after users began complaining on Sunday night that they were being forbidden access. "That's the problem – we still have no official information," he said.

A spokesman for Roskomnadzor, Russia's federal media monitoring agency, told RIA-Novosti that pages defining marijuana and bongs had prompted a request for the ban by Russia's federal drugs control agency.

Homak blamed the ban on bureaucratic incompetence. "It's because we're popular – some official probably Googled "marijuana" and we were one of the first sites to come up," he said. The website gets 120,000 unique visitors a day.

The website had joined a campaign that included the Russian versions of Wikipedia, Google and blogging platform LiveJournal, warning of the law's potential misuse before its adoption in July. Wikipedia warned that the law "will lead to the creation of a Russian analogue to China's Great Firewall".

"We didn't think it would be like this," Homak said. "The law is not worked through – no one knows who to answer to, or for what. It's a clusterfuck."

The administrator of the anonymous 2ch site, who only identified himself by his nickname Abu, also said the site had received no warning. He said he feared the weekend move to ban the popular sites boded ill for the future. "I fear that some idiots who don't even know basics about the Internet will start to censor everything and everything, just thinking that they are doing the right thing," he said in an email interview. "Like it is said: 'The road to hell is paved with good intentions'."

Russian internet users reacted to the bans with outrage and sarcasm. One Russian Twitter user wrote: "They also need to ban Anna Karenina as suicide propaganda", adding a popular new hashtag: net censorship.