Herman Van Rompuy accepted the annual Charlemagne Prize at city hall in the western German city of Aachen on Thursday.

The 66-year-old Belgian politician was chosen by adjudicators for his "meaningful services as a mediator and consensus-builder, and also as an important figure setting the tone for European unity."

The former Belgian prime minister, also a keen writer of haiku poems, was appointed as the first European Council president in 2009.

At the award ceremony, which was overshadowed by recent European elections with strong showings for right-wing parties in several countries, Van Rompuy addressed the current tensions in Ukraine and the east of Europe.

"Destabilization from our shared neighbor Russia is not acceptable," Van Rompuy said, adding that it was doubly regrettable because Russia "is certainly a part of European civilization, of European culture."

Kyiv's Yatsenyuk guest speaker

Ukraine's interim Prime Minister Arseniy Yatsenyuk was a guest speaker at the ceremony, along with the prime ministers of Moldova, Iurie Leanca, and Georgia, Irakli Garibashvili. Yatsenyuk, who met with German Chancellor Angela Merkel on Wednesday, also spoke critically, but without explicitly naming Russia.

"Nobody has the right to abuse the UN Charter and draw up new borders and erect new walls in Europe," Yatsenyuk said, also thanking Van Rompuy for his personal engagement in diplomatic efforts in Ukraine.

"We must fight for peace and for our freedom," the interim Ukrainian leader said.

Van Rompuy saluted "the courage" of the three eastern European heads of government "during these tumultuous times," in one of a series of Twitter messages published to coincide with the ceremony.

Problem of EU perception?

He also addressed the difficult European Parliament election results from Sunday, with major gains for several euroskeptic of right-wing parties, saying a key problem for the bloc was one of perception.

"We've never really thought of Europe as a home, a shelter, and today we pay a price for it. Europe, the great 'opener' of opportunities is now perceived by many as an unwelcome 'intruder,' the friend of freedom and space is seen as a threat to protection and place," van Rompuy said in Aachen.

Anti-EU and far-right parties made heavy gains in the polls in several countries. Since Sunday's poll, Van Rompuy has been charged by EU leaders with starting the process of picking suitable candidates for top jobs in the European Commission, most notably a successor to Commission President Jose Manuel Barroso, in the aftermath of the inconclusive ballot - where no political bloc won a clear majority.

Van Rompuy also mentioned a positive EU development of recent years, the improved situation surrounding member states' soverign debt loads. He recalled a quote from the 2008 Charlemagne Prize winner, current German Chancellor Angela Merkel, who had said "if the euro fails then Europe will fail."

"It [the debt crisis] was the worst ever threat to Europe's unity, and together we have overcome it," Van Rompuy said. "We have won the battle."

The 2013 Charlemagne Prize went to Lithuanian President Dalia Grybauskaite, who won re-election for a second term in a runoff vote on Sunday, the same day as the bulk of the European Parliament elections.

msh/ipj (AFP, dpa, epd)