BERLIN: Germany's conservative opposition leader was set Friday to again seek far-right support in parliament on the flashpoint issue of immigration, after his first effort sparked widespread condemnation and street protests.

The move comes after a series of deadly attacks have darkened the mood in Germany over the arrival of millions of war refugees and other asylum seekers in recent years, ahead of February 23 elections.

Poll frontrunner and head of the conservative CDU Friedrich Merz has vowed to wrest the initiative back from the far-right Alternative for Germany (AfD) to call for a crackdown on immigration.

But he sparked outrage, large street protests and a chiding from his own party's veteran Angela Merkel when the CDU pushed a first motion through parliament Wednesday with backing from the AfD.

Chancellor Olaf Scholz, the Greens and other critics condemned the move for breaking post-war Germany’s long-established “firewall” against any cooperation with the extreme right.

Thousands took to the streets in multiple rallies on Thursday waving signs that read “Shame on you”, “Friedrich Merz is a security risk for our democracy” and “We are the firewall”.

While Wednesday's resolution was a non-binding call to restrict immigration, the proposal on Friday's agenda would have the force of law, marking another milestone in German politics.

- Spate of attacks -

The CDU and its Bavarian allies the CSU have proposed a so-called Influx Limitation Act which would restrict family reunions for rejected asylum seekers with stays of deportation.

It would also boost the powers of federal police to detain undocumented migrants, whom Merz wants to place in custody and send back as soon as possible.

The CDU-CSU has urged Scholz's Social Democrats and their allies the Greens to back the bill, but is ready to pass it if needed with the AfD and the smaller FDP and BSW parties.

Unlike Wednesday's motion, it would eventually become a law if passed by the upper house, although this is considered highly unlikely to happen before the election.

Migration and public security have shot back up the political agenda after a series of deadly attacks where the suspects have been asylum-seekers.

Last week a man used a kitchen knife to attack kindergarten toddlers in a park in the southern city of Aschaffenburg, killing a two-year-old child and a man who tried to save the children.

Police arrested a 28-year-old Afghan man, who had stayed despite a deportation order to Bulgaria, where he entered the EU, and who is now being held in a psychiatric institution.

In December, police arrested a Saudi man over a car-ramming attack in which an SUV barrelled through a crowded Christmas market, killing five and wounding hundreds in the eastern city of Magdeburg.

- 'Hurt refugee rights' -

The AfD -- which rails against immigration, Islam and multiculturalism and is close to right-wing populist forces abroad -- is polling at around 20 percent.

Merz has insisted he is not seeking active co-operation with the AfD and would not enter a coalition with them.

“I would be selling the soul of the CDU if I even thought about it,“ he said at a campaign event on Thursday.

“It would not be the Alternative for Germany but the final decline for Germany.”

He has nonetheless defended the unprecedented tactical use of AfD support in the national legislature, arguing that “a right decision doesn’t become wrong just because the wrong people agree to it”.

Aside from the firewall controversy, human rights groups have broadly slammed Merz's immigration proposals, arguing they would contravene EU and international law.

Amnesty International said “the attack in Aschaffenburg would not have been prevented” by the CDU’s bill, which “instead will only hurt the rights of refugees”.

“Two wrongs don’t make a right,“ said its Germany chapter’s general secretary Julia Duchrow, who also voiced fears of an increase in random police checks and “racial profiling”.