German Chancellor Angela Merkel vowed Wednesday there would be no tolerance for "shameful and vile" anti-migrant violence, facing down a noisy far-right protest during a visit to a refugee center.

About 200 people massed in the eastern town of Heidenau, some booing and shouting "traitor, traitor" and "we are the mob" as she arrived at the shelter, in a show of defiance over a record influx of asylum-seekers.

Ukraine said Tuesday that the leaders of Germany and France had agreed to back "firm" steps against Russia should pro-Moscow rebels hold disputed elections in the ex-Soviet state's separatist east.

A top aide to President Petro Poroshenko said German Chancellor Angela Merkel and French President Francois Hollande had agreed at trilateral talks in Berlin on Monday to a set of "red lines" Russia must not cross.

Germany scrambled Tuesday to quell a wave of anti-migrant violence, as a new case of suspected arson hit a planned refugee shelter just hours after Chancellor Angela Merkel described xenophobic protests as "vile".

A week before 130 refugees are due to move into a temporary shelter in a sports hall in Nauen, a town near Berlin, the building went up in flames.

A new wave of migrants began entering the European Union from Serbia Monday as the leaders of France and Germany called for a unified response to the continent's biggest migrant crisis since World War II.

The EU has been struggling to find a response to the unprecedented numbers arriving -- from the thousands landing on the shores of Greece and Italy to the hundreds risking their lives to climb onto trucks to travel from France to Britain.

German Chancellor Angela Merkel condemned "vile" violent demonstrations against refugees at the weekend, her spokesman said Monday, amid criticism she has failed to forcefully address anti-migrant sentiment.

After clashes erupted in eastern Germany over two nights between police and far-right thugs protesting the opening of a new center for refugees, Merkel's spokesman Steffen Seibert said Berlin would not stand for hostility against the newcomers.

At least 2,000 more migrants flooded overnight into Serbia in a desperate journey to try and go on to Hungary, the door into the European Union, a U.N. official said Monday.

At least 7,000 people -- mostly refugees from the brutal war in Syria -- have been registered so far in the last days in overwhelmed Serbia as Europe's worst refugee crisis in half a century rapidly worsens.

President Francois Hollande bestowed France's highest honor on a group of Americans and a Briton on Monday saying the whole world "admires their courage and cool composure" in overpowering a Moroccan gunman on a crowded train.

Anti-terror investigators were questioning the alleged attacker, 25-year-old Ayoub El Khazzani, who boarded the high-speed train in Brussels bound for Paris on Friday armed with a Kalashnikov assault rifle, a Luger automatic pistol, ammunition and a box-cutter.

Police in east Germany clashed late Friday with far-right activists protesting against the opening of a center for refugees, police said.

Several hundred people turned up in Heidenau, near Dresden, to demonstrate against the expected arrival of hundreds of refugees in a protest called by the far-right National Democratic Party.

Seventeen people were injured in a riot at a refugee shelter in central Germany over a torn Koran, police said Thursday, in fresh tensions as the country braces to host 800,000 asylum seekers this year.

Violence erupted after about 20 refugees in the overcrowded shelter went in pursuit of another resident late Wednesday, accusing him of ripping pages out of a Koran and throwing them in a toilet, local police said.

Germany said Wednesday it could not rule out Russian President Vladimir Putin would take part in a future round of talks over conflict-torn eastern Ukraine after speculation that Western leaders were snubbing him.

Chancellor Angela Merkel is hosting talks with France's President Francois Hollande and Ukrainian leader Petro Poroshenko on Monday, and analysts said the conspicuous absence of Putin underlined that relations were deteriorating as new violence flares in eastern Ukraine.