FILE PHOTO: Annegret Kramp-Karrenbauer, chairwoman of Germany's Christian Democratic Union (CDU), delivers a speech during a festivity to celebrate the 70th anniversary of the German Institute for Economic Research (Ifo) in Munich, Germany, June 6, 2019. REUTERS/Michael Dalder/File Photo

BERLIN (Reuters) - Chancellor Angela Merkel’s conservatives on Monday ruled out any form of cooperation with Alternative for Germany (AfD), saying the far-right party’s anti-immigrant rhetoric was contributing to an atmosphere of hate that encourages political violence.

The decision by the governing board of the Christian Democrats (CDU) to officially shun the AfD comes after the CDU leader said the populist party must share blame for the killing of pro-immigration conservative politician Walter Luebcke.

CDU chairwoman Annegret Kramp-Karrenbauer said last week that the AfD, the largest opposition party in the German parliament, was legitimizing a language of hate that was encouraging far-right sympathizers to resort to violence.

Prosecutors believe a far-right sympathizer detained last week shot Luebcke at close range on June 2.

The politician, who headed the regional government in the city of Kassel, was a hate figure on far-right internet forums critical of Merkel’s 2015 decision to welcome around a million refugees at the height of the refugee crisis.

“The unleashing of extreme-right violence including right-wing terrorism prospers in an atmosphere of rightist incitement on the Internet and social media,” the CDU said in its motion blocking any form of cooperation with the AfD.

Some CDU politicians, especially in eastern states where the AfD is strongest, have said the conservatives should not ostracize the far-right party and consider building coalitions with it at least on the regional level.

The AfD has rejected suggestions that its anti-immigration stance was to blame for Luebcke’s death and said its members were the victim of left-wing violence.

Merkel’s conservatives bled voters to the AfD in the 2017 national election as well as in regional votes. Polls show the AfD running neck-and-neck with the CDU in two of three eastern states that hold elections in Autumn.