German Chancellor Friedrich Merz will huddle Monday with his CDU party to discuss and digest their thumping defeat at the hands of the far-right AfD party in a state election in the ex-communist east.

The anti-immigration Alternative for Germany scored its biggest win yet Sunday with 44 percent of the vote in the Saxony-Anhalt, against about 18 percent for the centre-right CDU, according to broadcasters' projections.

The visibly dejected CDU state premier Sven Schulze said his campaign was not always helped by national government policies, saying that "we often faced headwinds, and that wasn't always easy".

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The ballot box triumph put the pro-Trump and Moscow-friendly AfD -- officially listed as "right-wing extremist" by Germany's domestic intelligence agency -- within reach of running its first-ever state government.