Vowing to take tough action against perpetrators of such attacks, top politicians sought to reassure the unprecedented number of migrants arriving in the country that far-right extremists did not represent Germany. “With regards to xenophobic violence, there can only be one answer: police, justice and, if possible for those we catch, prison as well,” said Vice Chancellor Sigmar Gabriel.

Merkel, who has been criticised for failing to forcefully address the wave of anti-migrant sentiment until this week, will on Wednesday visit a refugee centre targeted by far-right extremists and neo-Nazis in the eastern town of Heidenau.

Germany is expecting to receive a record number of 800,000 asylum-seekers this year, four times higher than the number in 2014.

The sudden surge in people coming from war zones such as Syria as well as countries that are not at war like Albania and Kosovo has left the authorities struggling to cope.

It has also exposed anti-migrant sentiment, particularly in eastern Germany, which still lags behind the western part of the country in terms of jobs and opportunities 25 years after reunification.

The latest case of suspected arson hit a temporary shelter in a sports hall in Nauen, a town near Berlin, just a week before 130 refugees are due to move in. Police said the speed of the flames ripping through the site early Tuesday suggested arson was the cause.

The state president of Brandenburg, where Nauen is located, Dietmar Woidke urged residents to “distance yourself from xenophobic mobs”.

“Be it agitations against foreigners or attacks against people in need in Heidenau or the hindering of the arrival of refugees in Nauen by arson, such action is shameful and unworthy of Germany,” he said in a statement.

Over the weekend violent protests broke out as patriots and demonstrated against a refugee shelter in Heidenau.

Merkel also had strong words on Monday for those marching alongside in support of the anti-migrant cause. “It is vile for far-right extremists and neo-Nazis to try to spread their hollow, hateful propaganda but it is just as shameful for citizens including families with children to join them” in their protests, she said in her strongest statement to date about a wave of anti-refugee protests in eastern Germany.

Justice Minister Heiko Maas on Tuesday said the extremists “have no place in the street but before the courts”. But he ruled out the establishment of security barricades around refugee shelters, telling ARD television: “I don’t want to live in a country (where such measures have to be taken) for people to feel secure”.

– A flood of threats – As Europe’s top economy braces to receive an unprecedented number of asylum seekers this year, the number of migrant hate crimes appear to have increased in tandem.