The European Union (EU) has announced that it is making a U-turn on its generous migrant policy, instructing Germany, its biggest member, to stop accepting more migrants and tighten control of its borders.

With Europeans up in arms amid mounting protests against the perceived Muslim invasion of their continent, EU Council President Donald Tusk on Monday called on German Chancellor Angela Merkel to put an end to her government's open-door policy on migrants and "protect the external European borders decisively," the Daily Express reported.

"I understand if Germany, for historical reasons, has difficulty implementing a strict regime on its borders," Tusk told the German newspaper Welt Am Sonntag, alluding to Germany's wartime guilt which the nation wants to cast out by adopting liberal policies.

However, the EU chief also said "Germany's leadership responsibility within the EU also requires it to protect the external European borders decisively if necessary, in accordance with pan-European unity."

Tusk described Germany's response to the migrant crisis as "the most liberal and tolerant in European history."

Merkel was initially congratulated at home and abroad for opening Germany's doors to the migrants, many of whom were from war-ravaged Syria. But as the flow of migrants continued stretching German generosity to the limit to the point of undermining the peace and security of its own citizens, Merkel has come under withering fire.

But on Monday, Merkel drew praise from Tusk in his speech in Berlin to mark the 26th anniversary of the fall of the Berlin Wall, Reuters reported.

"Those who believe that Germany is too open, too tolerant, too liberal, forgot to do their homework about our tragic history," said Tusk, a former Polish prime minister.

"Do you want a Germany that is open, tolerant, compassionate, sympathising with the weaker and the poorer, in other words the Germany of Angela Merkel, or a Germany which is closed, cold and ruthless? There is only one answer," he said.

This is the reason, Tusk said, why other European states should now show solidarity towards Germany "in these difficult and testing times."

Germany has already accepted some 758,000 migrants since January this year. If border controls are not put in place, officials expect the figure to break the million mark before the year is over.

At the same time, Tusk urged Germany to lead in securing Europe's borders and protect Europe against a rise of radical populism.

"In the face of the unprecedented scale of migrants flowing to Europe, we have to say in simple terms: Europe is not able to accept all the people willing to come to our continent."

"Let us not fool ourselves. The fall of the Berlin wall did not automatically abolish the need for borders as such," he said.

Merkel has been criticised for unwittingly encouraging more migrants to come to Germany by announcing that her government is not imposing limits on the number of migrants it would accept.

Tusk was referring to the humanitarian and political chaos in Germany that has led to a rise in support for the anti-immigrant Alternative for Germany (AfG) party.

The far-right AfD has attacked Merkel's policy, calling it "asylum chaos." It accused Merkel of "people smuggling" for allowing thousands of asylum seekers into Germany after they got stuck on the Hungarian border.