Germany's fight against hate speech has reached Mark Zuckerberg himself.

A German prosecutor has named Zuckerberg,Korean College Girl Room Salon Facebook Chief Operating Officer Sheryl Sandberg and European Facebook executives in a preliminary investigation, according to German media.

The investigation was prompted by a lawsuit filed by Chan-jo Jun, an attorney who filed a similar complaint a year ago. This one, which said that Facebook failed to remove hate speech even once it was aware of the violations of German law, singled out Zuckerberg by name.

“We are not commenting on the status of a possible investigation but we can say that the allegations lack merit and there has been no violation of German law by Facebook or its employees," Facebook said in a statement. "There is no place for hate on Facebook. We work closely with partners to fight hate speech and foster counter speech.“

The investigation and lawsuit are tied to a broader crackdown against online hate speech. A German justice minister said earlier this week that Facebook and Twitter would both be required to improve their responses to hate speech or face legal action, the Associated Press reported.

Germany has strict laws surrounding hate speech. The laws, a result of Germany's history, protect minority groups from incitement to hatred or harassment.

While Germany's hate speech laws single out anti-Semitism, the issue has come to public attention recently over speech targeted at the wave of refugees entering Germany.

A study over the summer found that Facebook removed 46 percent of posts flagged as hate speech and Twitter removed 1 percent, the AP said.

That's not enough for Germany.

In the United States, Twitter is usually the social network to earn criticism for its lack of response to hate speech. Facebook, meanwhile, is more often called out for censorship.

German media didn't mention any Twitter executives named in an investigation.