French police have opened a criminal investigation into a recent surge of anti-Semitic messages posted on Twitter, AFP reported. 

Last month anti-racism organizations filed complaints against the micro-blogging site, claiming that numerous tweets had breached French law prohibiting incitement to racial hatred.

The police probe, which is still in a preliminary phase, will focus on the possibility of ordering Twitter to divulge details about users who post offensive comments.

France's Union of Jewish Students (UEJF) has been urging Twitter to exercise tighter control over the site following a wave of anti-Semitic messages posted under the hashtag #unbonjuif , meaning “a good Jew”.

The tweet prompted thousands of Twitter users to enter what the French daily Le Monde termed “a competition of anti-Semitic jokes”, with one user posting a picture of an emaciated Jewish woman in a Nazi concentration camp as the interpretation of "a good Jew," while others tweeted that “a good Jew is a dead Jew.”

A Twitter spokesperson refused at the time to comment directly on the tweets and reiterated the company's policy that it "does not mediate content".

"If we are alerted to content that may be in violation of our terms of service, we will investigate each report and respond according to the policies and procedures outlined in our support pages," the spokesman, according to News 24.

The site has said it would not relinquish details of account holders unless ordered to do so by a judge.

In October, the site suspended the account of a neo-Nazi group in Germany following a request from the government in Berlin. It was the first time Twitter had acted on a request of that nature from a government.