BERLIN, Sept. 3 (Xinhua) -- Thomas Oppermann (SPD), deputy president of the German federal parliament (Bundestag), has on Monday called for the country's Office for the Protection of the Constitution (BfV) to investigate links between the Alternative for Germany (AfD) party and right-wing extremists.

Speaking to the newspaper WELT in the wake of a widely-publicized series of far-right riots in the town of Chemnitz, the German Social Democrat (SPD) politician warned of growing signs that the AfD was cooperating with Neonazis and other far-right activists who were plotting to overthrow Germany's constitutional order.

"The refugee question is dividing society and the AfD is riding this wave in a more and more radical fashion," Oppermann said. He argued that the two groups appeared to have agreed on a "division of labor" which justified the monitoring of the AfD by German intelligence services.

AfD politicians helped organize several demonstrations inspired by the alleged murder of a German by two foreigners in Chemnitz. Following clashes with police, anti-Nazi protestors, and civilians, the party leadership defended what it saw as understandable outbursts of anger.

"It is legitimate to go berserk after this kind of crime," AfD deputy leader Alexander Gauland said at the time.

The events led Ernst Walter, president of the Federation of German Police Officers (BDK), to issue a dramatic warning that security officers could no longer guarantee the rule of law in parts of the country.

"The AfD has let its mask slip once again when its leader (Alexander Gauland) describes these incidents as 'normal anger'. Whoever speaks this way attacks the basic principles of the rule of law and incites violence," Oppermann told WELT.

Nevertheless, the SPD politician highlighted that Germany's drift to the right could not be halted with repressive measures alone. He urged the federal government to enshrine a "realistic and controlled" migration policy in new legislation, as well as to speed up asylum application procedures, protect European Union (EU) external borders and invest more in Africa.

The comments by Oppermann were made shortly after Christian Democratic Union (CDU) and Christian Social Union (CSU) parliamentary faction leader Volker Kauder made an appeal for democratic-minded Germans to confront the AfD.

"The AfD wants to attack our state," Kauder told WELT. He specifically referred to a recent Facebook post by a regional AfD party organization threatened journalists to "start telling the truth" to prevent a looming "revolution", or otherwise face the prospect of "being dragged onto the streets when publishing houses and radio stations are stormed."

Left party (Linke) parliamentary faction leader Dietmar Bartsch praised Kauder's intervention as a "welcome contrast" to the relative silence of interior minister Horst Seehofer (CSU) on the events of Chemnitz. Similarly, Green party (Gruene) secretary Michael Kellner said that he was encouraged by the "clear words by Kauder on the AfD and his sincere concern about our democracy."