(CNN) A far-right party scored its strongest-ever results in two key state elections in eastern Germany on Sunday, finishing second behind the country's major parties on the same day that Europe marked the 80th anniversary of the Nazi invasion of Poland.

The results represent a blow to Merkel's ruling coalition with the SPD, and will be viewed as a victory for the AfD, which took 27.5% of votes in Saxony and 23.5% in Brandenburg -- a significant increase on state elections five years ago, with the party almost tripling its share in Saxony and doubling it in Brandenburg.

The AfD became the first far-right party to enter Germany's national parliament in almost 60 years when it came in third place overall in federal elections in 2017.

Sunday's results came on the same day that Germany's President Frank-Walter Steinmeier asked Poland for forgiveness 80 years after Nazi Germany's invasion.

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