European Commission chief Jean-Claude Juncker on Monday urged German Chancellor Angela Merkel to form a strong coalition government as soon as possible to help "shape the future" of the EU.
Merkel met with her party on Monday - the day after winning a fourth term - with a far weaker mandate in a general election, facing the double headache of an emboldened nationalist opposition party and thorny coalition talks.
Juncker spoke by telephone to Merkel and wrote to her to congratulate on her "historic victory", his spokesman Margaritis Schinas told reporters in Brussels.
"In the light of the important global challenges, Europe needs a strong German government now more than ever, one able to actively shape the future of our continent," Schinas quoted Juncker as saying in the letter.
"And in his letter president Juncker expresses his belief that the negotiations on the coalition government will contribute to that effect."
Asked about the success in the election of the anti-Islam Alternative for Germany (AfD) party, which became the third strongest party, Schinas said that "the commission has faith in democracy".
Juncker stressed the "need to avoid complacency, distinguish between those questioning our policies from those who are simply out to destroy the European Union, and the need to... face up to the populist discourse and explain Europe better," Schinas said.
French President Emmanuel Macron also congratulated German Chancellor Angela Merkel on her election win on Monday, promising that the two key European partners would keep up their "essential cooperation".
"I called Angela Merkel to congratulate her. We will continue our essential cooperation with determination for Europe and for our countries," Macron said on Twitter.
Danish prime minister Lars Løkke Rasmussen tweeted “congratulations to Chancellor Merkel. We need stability in Europe. I'm looking forward to us working together.”
But an MP in Rasmussen's governing Liberal (Venstre) party caused internal division after posting a message that appeared to show support for the AfD.
“It was a catastrophe that Angela Merkel, with the words ‘Wir schaffen das' (we can do it) let a million asylum seekers and migrants into Europe. That's why I'm happy that there is now better balance in the German parliament,” Marcus Knuth said, angering party colleagues.
Sebastian Kurz, the charismatic young Foreign Minister of Austria, who many tip to become the next Chancellor in Vienna, decided to focus on the AfD success.
“That was no surprise,” Kurz said. “There are many people in Germany dissatisfied with the government's refugee policies.”
The AfD also won support from other far-right movements.
Marine le Pen, leader of le Front National in France said that it was “a historic result.”
“That is a new sign that European people are waking up.”