FACEBOOK is more like a "version of the dark web" than a social networking site, Chicago police officers say.

Cops arrested 53 people on Monday as part of "Operation FaceBOOKED", a two-year sting operation to infiltrate secret Facebook groups illegally selling guns and drugs, the Chicago Tribune reported.

4 Police seized guns and drugs worth thousands of dollars in a Facebook sting operation Credit: @AJGuglielmi

4 53 people have been arrested in the undercover operation, which started in 2017 Credit: @AJGuglielmi

Although drug-dealing and private gun sales go against Facebook's commerce policies, CPD officials accused the company of "turning a blind eye" to the problem.

"Facebook claims to monitor these groups but CPD detectives have labeled these private hidden sites a version of the dark web that is more accessible to everyday users," First Deputy Superintendent Anthony Riccio said at a press conference in Chicago on Tuesday.

Police recovered four handguns, two shotguns, and a high-powered rifle worth a total of $4,100 and 23 types of narcotics totaling $105,000.

Facebook agreed to remove groups flagged by police during the operation but won't block individual members due to member privacy, according to Riccio.

"Facebook often cites privacy concerns when they're confronted with the facts of our investigation," he said.

4 CPD accused Facebook of facilitating the sale of illegal guns and drugs Credit: AP:Associated Press

"The truth is, Facebook is harboring criminals. These criminals know how to use the privacy Facebook affords them, and they profit from the sale of drugs and dangerous guns."

CPD also criticized the social media giant for banning fake undercover police profiles.

Fake accounts aren't allowed under Facebook's authenticity policy.

Operation FaceBOOKED began in December 2017, when police were tipped off by an informant that drugs and weapons were regularly sold in private Facebook groups.

These groups are hidden, making them invisible to anyone who isn't either already a member or personally invited in, according to Riccio.

Facebook's site says doesn't allow the purchase, sale or trade of firearms, ammunition and explosives between private users.

4 Facebook users are banned from privately selling guns or advertising them for sale Credit: @AJGuglielmi

Facebook spokeswoman Sarah Pollack told CNN illicit drug and firearms sales have "no place" on the platform.

She noted that the website catches more than 97% of drug sale content and more than 93% of firearm sales content before it's reported.

Even though the social network banned the private sale of guns in January 2016, users have found ways to flout the rules.

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A 27-year-old man arrested in the sting operation on Monday was booked in a 2017 CPD operation of Facebook, Riccio said.

Rather than focus on user privacy, Interim Superintendent Charlie Beck said the social media juggernaut should be more concerned about safety.

"Another person's rights have to stop when the safety of another individual comes in jeopardy, and that's what laws are all about."