The Alternative for Germany (AfD) became the first far-right party to win a state legislature election in Germany since World War Two with its result in weekend voting in Thuringia. It came a close second behind the conservatives in Saxony, projections late on Sunday showed.
But the AfD, deemed "right-wing extremist" by security officials in both of the east German states, is unlikely to be able to govern as other parties have so far refused to collaborate with it to form a majority.
Still, the nationalist, anti-migration and Russia-friendly party could end up with enough seats in both states to block decisions requiring a two-thirds majority such as the appointment of judges or top security officials, giving it unprecedented power.
German Chancellor Olaf Scholz called the results of two regional elections that saw big wins for the far-right AfD and losses for his coalition "bitter" and urged mainstream parties to form governments without "right-wing extremists".
"The results for the AfD in Saxony and Thuringia are worrying," Scholz said in a statement to Reuters. He clarified he was talking as a lawmaker for his centre-left Social Democrats (SPD).
"Our country cannot and must not get used to this. The AfD is damaging Germany. It is weakening the economy, dividing society and ruining our country's reputation."
With a year to go until Germany's national election, the results on Sunday punished Scholz's fractious coalition, which could aggravate infighting.
Losing votes
All three ruling parties lost votes, with only his SPD comfortably clearing the 5% threshold needed to stay in the two states' parliaments.
Populist leftist newcomer, the Sahra Wagenknecht Alliance (BSW), founded by a former member of the East German Communist Party, did better than all of three coalition partners in its first state elections, coming in third place.
"Sunday's election results are bitter - for us too," Scholz said. But he noted that the more dire predictions, that the SPD might fall out of a state parliament for the first time, had not materialized.
Junior coalition partners the Greens and pro-business Free Democrats both fell out of the Thuringia state assembly.
Sunday's results could also pressure the government to be tougher on immigration and intensify the debate over support for Ukraine, issues that dominated the campaign.