(Bloomberg) -- European leaders gave Kosovo and Serbia a list of clear tasks to end the worst outbreak of violence in a decade, saying they must ease tensions or face serious consequences.

France’s Emmanuel Macron and German Chancellor Olaf Scholz told Kosovo it must hold do-over local elections in its troubled north and Serbia must ensure that its ethnic kin in Kosovo take part, the French president said late on Thursday. 

Both sides must also work on setting up a mechanism called an Association of Serb Municipalities that was originally agreed to a decade ago in European Union-brokered talks to give Serbs, who are the dominant population in northern Kosovo, more autonomy over economic development, education and other aspects of their lives.

“Failure to do so will have serious consequences for our relations,” EU foreign policy chief Josep Borrell said in a tweet late Thursday.

The unusually stark language underscores Europe’s diminishing patience with the two Balkan nations after years of grinding negotiations that have produced few results. The proposals — the first concrete demands from allies aimed at ending the crisis — are to be discussed with both sides next week.

Dozens of NATO peacekeepers and Serb protesters were injured over the past week in unrest sparked by Kosovo’s resolve to install newly appointed, ethnic-Albanian mayors into their offices in the north of the country. They won their posts after local Serbs boycotted elections, acting on guidance from the government in neighboring Serbia.

Read More: Violence in Kosovo Exposes Perilous Limbo in Europe’s Powder Keg

Borrell, Macron and Scholz met with the presidents of Kosovo and Serbia on Thursday in Moldova.

“What we asked both parties is very simple: The organization as soon as possible of new elections in these four municipalities,” Macron told reporters. “Commitment from Kosovo. Clear participation by the Serbian side in these elections.”

Meeting the demands would require major concessions from both sides.

For Belgrade, it would mean actively encouraging Serbs in Kosovo to vote after the previous ballot drew turnout of just 3%. 

Kosovar Prime Minister Albin Kurti has said the four mayors were appointed legitimately. He has refused to bow to pressure from Serb protesters to remove them and has blamed Serbian President Aleksandar Vucic of stoking the unrest.

Scholz didn’t sound very optimistic on resolving the current tensions. A resolution would require “courage from all sides,” given how unpopular it would be in both countries, he said.

“This is a very serious issue and we have therefore also addressed the issue with all seriousness,” Scholz said after the meeting. “We will see what can be achieved.”

--With assistance from Arne Delfs.

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