German Chancellor Angela Merkel delivers a speech during her visit to the former German Nazi death camp Auschwitz-Birkenau in Oswiecim, Poland on Friday. Photo: AFP

With growing dangers from far-right extremist groups and torrents of threats against politicians, Germany is set to toughen online speech laws and tighten the screws on social networks.

Ministers in Chancellor Angela Merkel's government are expected to wave through a new package of measures on Wednesday, days after 12 men were arrested for planning deadly attacks on mosques, communicating in part via chat groups.

"In future, those who make threats or spread hate online will be prosecuted more toughly and more effectively," German Justice Minister Christine Lambrecht said on her ministry's website.

One headline measure in the draft law will step up the pressure on social networking firms like Facebook to quickly remove the offending content.

In future, the Silicon Valley giants will also have to report certain types of illegal posts to the federal police, who will be able to pass on actionable data to prosecutors.

Covered under such rules would be neo-Nazi propaganda or plans to commit a terrorist attack.

But people approving of crimes, making death or rape threats or sharing child pornography images could also be caught in the widened net.

Social media platforms that refuse to cooperate will face fines of up to 50 million euros ($54 million).

On top of the new reporting processes, Berlin wants to toughen potential sentences, including up to three years in prison for online death or rape threats.

The draft law would sharpen sentences still further for crimes arising from an anti-Semitic motive, which the justice ministry says have increased 40 percent since 2013.

But there are limits to the rules, leaving it up to the person affected to pursue cases of insult or libel.

In the most serious cases, such as terrorism or murder, network operators will be required to give up users' passwords to the authorities if ordered to by a judge - including if they are encrypted, a typical security measure.

Ministers' plans have not gone unopposed in Germany, where debate is fierce between those who value online anonymity as a shield against the state and those who see unregulated online spaces as a threat.

AFP